Raw File Compression

Posted on March 14, 2016 by Andrew Astbury

Raw File Compression.

Today I’m going to give you my point of view over that most vexatious question – is LOSSLESS raw file compression TRULY lossless?

I’m going to upset one heck of a lot of people here, and my chances of Canon letting me have any new kit to test are going to disappear over the horizon at a great rate of knots, but I feel compelled to post!

What prompts me to commit this act of potential suicide?

It’s this shot from my recent trip to Norway:

Direct from Camera

Processed in Lightroom

I had originally intended to shoot Nikon on this trip using a hire 400mm f2.8, but right at the last minute there was a problem with the lens that couldn’t be sorted out in time, so Calumet supplied me with a 1DX and a 200-400 f4 to basically get me out of a sticky situation.

As you should all know by now, the only problems I have with Canon cameras are their short Dynamic Range, and Canons steadfast refusal to allow for uncompressed raw recording.

The less experienced shooter/processor might look at the shot “ex camera” and be disappointed – it looks like crap, with far too much contrast, overly dark shadows and near-blown highlights.

Shot on Nikon the same image would look more in keeping with the processed version IF SHOT using the uncompressed raw option, which is something I always do without fail; and the extra 3/4 stop dynamic range of the D4 would make a world of difference too.

Would the AF have done as good a job – who knows!

The lighting in the shot is epic from a visual PoV, but bad from a camera exposure one. A wider dynamic range and zero raw compression on my Nikon D4 would allow me to have a little more ‘cavalier attitude’ to lighting scenarios like this – usually I’d shoot with +2/3Ev permanently dialled into the camera. Overall the extra dynamic range would give me less contrast, and I’d have more highlight detail and less need to bump up the shadow areas in post.

In other words processing would be easier, faster and a lot less convoluted.

But I can’t stress enough just how much detrimental difference LOSSLESS raw file compression CAN SOMETIMES make to a shot.

Now there is a lot – and I mean A LOT – of opinionated garbage written all over the internet on various forums etc about lossless raw file compression, and it drives me nuts. Some say it’s bad, most say it makes no difference – and both camps are WRONG!

Sometimes there is NO visual difference between UNCOMPRESSED and LOSSLESS, and sometimes there IS. It all depends on the lighting and the nature of the scene/subject colours and how they interact with said lighting.

The main problem with the ‘it makes no difference’ camp is that they never substantiate their claims; and if they are Canon shooters they can’t – because they can’t produce an image with zero raw file compression to compare their standard lossless CR2 files to!

So I’ve come up with a way of illustrating visually the differences between various levels of raw file compression on Nikon using the D800E and Photoshop.

But before we ‘get to it’ let’s firstly refresh your understanding. A camera raw file is basically a gamma 1.0, or LINEAR gamma file:

Linear (top) vs Encoded Gamma

The right hand 50% of the linear gamma gradient represents the brightest whole stop of exposure – that’s one heck of a lot of potential for recording subtle highlight detail in a raw file.

It also represents the area of tonal range that is frequently most effected by any form of raw file compression.

Neither Nikon or Canon will reveal to the world the algorithm-based methods they use for lossless or lossy raw file compression, but it usually works by a process of ‘Bayer Binning’.

Bayer_Pattern

If we take a 2×2 block, it contains 2 green, 1 red and 1 blue photosite photon value – if we average the green value and then interpolate new values for red and blue output we will successfully compress the raw file. But the data will be ‘faux’ data, not real data.

The other method we could use is to compress the tonal values in that brightest stop of recorded highlight tone – which is massive don’t forget – but this will result in a ’rounding up or down’ of certain bright tonal values thus potentially reducing some of the more subtle highlight details.

We could also use some variant of the same type of algorithm to ‘rationalise’ shadow detail as well – with pretty much the same result.

In the face of Nikon and Canons refusal to divulge their methodologies behind raw file compression, especially lossless, we can only guess what is actually happening.

I read somewhere that with lossless raw file compression the compression algorithms leave a trace instruction about what they have done and where they’ve done it in order that a raw handler programme such as Lightroom can actually ‘undo’ the compression effects – that sounds like a recipe for disaster if you ask me!

Personally I neither know nor do I care – I know that lossless raw file compression CAN be detrimental to images shot under certain conditions, and here’s the proof – of a fashion:

Let’s look at the following files:

Image 1: 14 bit UNCOMPRESSED

Image 2: 14 bit UNCOMPRESSED

Image 3: 14 bit LOSSLESS compression

Image 4: 14 bit LOSSY compression

Image 5: 12 bit UNCOMPRESSED

Yes, there are 2 files which are identical, that is 14 bit uncompressed – and there’s a reason for that which will become apparent in a minute.

First, some basic Photoshop ‘stuff’. If I open TWO images in Photoshop as separate layers in the same document, and change the blend mode of the top layer to DIFFERENCE I can then see the differences between the two ‘images’. It’s not a perfect way of proving my point because of the phenomenon of photon flux.

Photon Flux Andy??? WTF is that?

Well, here’s where shooting two identical 14 bit uncompressed files comes in – they themselves are NOT identical!:

The result of overlaying the two identical uncompressed raw files (above left) – it looks almost black all over indicating that the two shots are indeed pretty much the same in every pixel. But if I amplify the image with a levels layer (above right) you can see the differences more clearly.

So there you have it – Photon Flux! The difference between two 14 bit UNCOMPRESSED raw files shot at the same time, same ISO, shutter speed AND with a FULLY MANUAL APERTURE. The only difference between the two shots is the ratio and number of photons striking the subject and being reflected into the lens.

Firstly 14 Bit UNCOMPRESSED compared to 14 bit LOSSLESS (the important one!):

14 bit UNCOMPRESSED vs 14 bit LOSSLESS

Please remember, the above ‘difference’ image contains photon flux variations too, but if you look carefully you will see greater differences than in the ‘flux only’ image above.

The two images above illustrate the differences between 14 bit uncompressed and 14 bit LOSSY compression (left) and 14 bit UNCOMPRESSED and 12 bit UNCOMPRESSED (right) just for good measure!

In Conclusion

As I indicated earlier in the post, this is not a definitive testing method, sequential shots will always contain a photon flux variation that ‘pollutes’ the ‘difference’ image.

I purposefully chose this white subject with textured aluminium fittings and a blackish LED screen because the majority of sensor response will lie in that brightest gamma 1.0 stop.

The exposure was a constant +1EV, 1/30th @ f 18 and 100 ISO – nearly maximum dynamic range for the D800E, and f18 was set manually to avoid any aperture flicker caused by auto stop down.

You can see from all the ‘difference’ images that the part of the subject that seems to suffer the most is the aluminium part, not the white areas. The aluminium has a stippled texture causing a myriad of small specular highlights – brighter than the white parts of the subject.

What would 14 bit uncompressed minus 14 bit lossless minus photon flux look like? In a perfect world I’d be able to show you accurately, but we don’t live in one of those so I can’t!

We can try it using the flux shot from earlier:

But this is wildly inaccurate as the flux component is not pertinent to the photons at the actual time the lossless compression shot was taken. But the fact that you CAN see an image does HINT that there is a real difference between UNCOMPRESSED and LOSSLESS compression – in certain circumstances at least.

If you have never used a camera that offers the zero raw file compression option then basically what you’ve never had you never miss. But as a Nikon shooter I shoot uncompressed all the time – 90% of the time I don’t need to, but it just saves me having to remember something when I do need the option.

raw file compression

Would this 1DX shot be served any better through UNCOMPRESSED raw recording? Most likely NO – why? Low Dynamic Range caused in the main by flat low contrast lighting means no deep dark shadows and nothing approaching a highlight.

I don’t see it as a costly option in terms of buffer capacity or on-board storage, and when it comes to processing I would much rather have a surfeit of sensor data rather than a lack of it – no matter how small that deficit might be.

Lossless raw file compression has NO positive effect on your images, and it’s sole purpose in life is to allow you to fit more shots on the storage media – that’s it pure and simple. If you have the option to shoot uncompressed then do so, and buy a bigger card!

What pisses my off about Canon is that it would only take, I’m sure, a firmware upgrade to give the 1DX et al the ability to record with zero raw file compression – and, whether needed or not, it would stop miserable grumpy gits like me banging on about it!

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Autofocus Guide for Long Lens Bird in Flight Photography

Posted on August 15, 2015 by Andrew Astbury

GX2R2055-Edit-2

My Autofocus Guide for Bird in Flight Photography is finished and available for download in my online store – here, priced £29.00

The download is in the no-frills .pdf format.

This is my ‘real world’ guide to Canon & Nikon Autofocus which is specifically aimed at photographers using long lenses for Bird in Flight photography.

I sell my full resolution wildlife and natural history images every day via the various global image libraries to which I am a contributor. The largest percentage of these sales are Birds in Flight.

Image libraries demand tack sharp, full resolution uploads from their contributors; even marginal sharpness will result in an image being rejected by Quality Control.

A large male White-tailed eagle, locally known as “Brutus”, carrying a very large Coalfish.

In this guide, I take you right back to the basics of subject speed and distance; and how this impacts on our choice of camera body and lens focal length and working aperture.

A Red Kite in a fast dive against a blue sky.

You’ll learn how phase detection autofocus works – only by really understanding how your autofocus system works, and what its control settings actually do, will you truly be able to control it in the way you need to for the particular task at hand.

I give you exposure and autofocus control settings for both Canon and Nikon, based on ‘real world’ full resolution images – settings that actually work, and do the job you expect them to do.

We also discover the various ‘tips ‘n tricks’ we need to know to help the autofocus system do the job we are asking it to do.

We also look at the short-comings of both the Nikon and Canon systems, and how to work around them in order to produce tack sharp images of birds in flight – HAND HELD – forget that tripod; you can’t move fast enough with one!

Photographers who have read this guide as it was being written have called it ‘the definitive guide’. I’m not going to be so big-headed as to promote it as such myself, but I will say that it’s taken a while to produce, is pretty darn thorough, and I have the shots to prove it!

Available for purchase in my online store right now.

Please Note: This document relates to LONG LENS continuous auto focus tracking in Nikon AFC and Canon AI Servo modes in conjunction with continuous shooting modes on Nikon D4/4S and Canon 1Dxbodies with v2 firmware or higher, and is primarily related to capturing Birds in Flight and other fast-paced wildlife action photography.
Canon 5DMk3/7DMk2 users will also find this guide very useful, as will non-wildlife shooters.

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Image Sharpness

Posted on April 16, 2015 by Andrew Astbury

Image Sharpness

I spent the other afternoon in the Big Tower at Gigrin, in the very pleasant company company of Mr. Jeffrey “Jeffer-Cakes” Young. Left arm feeling better yet Jeff?

I think I’m fairly safe in saying that once feeding time commenced at 3pm it didn’t take too long before Jeff got a firm understanding of just how damn hard bird flight photography truly is – if you are shooting for true image sharpness at 1:1 resolution.

I’d warned Jeff before-hand that his Canon 5Dmk3 would make his session somewhat more difficult than a 1Dx, due to it’s slightly less tractable autofocus adjustments. But that with his 300mm f2.8 – even with his 1.4x converter mounted, his equipment was easily up to the job at hand.

I on the other hand was back on the Nikon gear – my 200-400 f4; but using a D4S I’d borrowed from Paul Atkins for some real head-to-head testing against the D4 (there’s a barrow load of Astbury venom headed Nikon’s way shortly I can tell you….watch this space as they say).

Amongst the many topics discussed and pondered upon, I was trying to explain to Jeff the fundamental difference between ‘perceived’ and ‘real’ image sharpness.

Gigrin is a good place to find vast armies of ‘photographers’ who have ZERO CLUE that such an argument or difference even exists.

As a ‘teacher’ I can easily tell when I’m sharing hide space with folk like this because they develop quizzical frowns and slightly self-righteous smirks as they eavesdrop on the conversation between my client and I.

“THEY” don’t understand that my client is wanting to achieve the same goal as the one I’m always chasing after; and that that goal is as different from their goal as a fillet of oak-smoked Scottish salmon is from a tin of John West mush.

I suppose I’d better start explaining myself at this juncture; so below are two 800 pixel long edge jpeg files that you typically see posted on a nature photography forum, website or blog:

image sharpness, Andy Astbury, Wildlife in Pixels, Red Kite

IMAGE 1. Red Kite – Nikon D4S+200-400 f4 – CLICK IMAGE to view properly.

Click the images to view them properly.

IMAGE 2. Red Kite – Nikon D4S+200-400 f4 – CLICK IMAGE to view properly.

“THEY” would be equally as pleased with either…..!

Both images look pretty sharp, well exposed and have pretty darn good composition from an editorial point of view too – so we’re all golden aren’t we!

Or are we?

Both images would look equally as good in terms of image sharpness at 1200 pixels on the long edge, and because I’m a smart-arse I could easily print both images to A4 – and they’d still look as good as each other.

But, one of them would also readily print to A3+ and in its digital form would get accepted at almost any stock agency on the planet, but the other one would most emphatically NOT pass muster for either purpose.

That’s because one of them has real, true image sharpness, while the other has none; all it’s image sharpness is perceptual and artificially induced through image processing.

Guessed which is which yet?

IMAGE 1 at 1:1 native resolution – CLICK IMAGE to view properly.

Image 1. has true sharpness because it is IN FOCUS.

IMAGE 2 at 1:1 native resolution – CLICK IMAGE to view properly.

And you don’t need glasses to see that image 2 is simply OUT OF FOCUS.

The next question is; which image is the cropped one – number 2 ?

Wrong…it’s number 1…

Image 1 uncropped is 4928 pixels long edge, and cropped is 3565, in other words a 28% crop, which will yield a 15+ inch print without any trouble whatsoever.

Image 2 is NOT cropped – it has just been SHRUNK to around 16% of its original size in the Lightroom export utility with standard screen output sharpening. So you can make a ‘silk purse from a sows ear’ – and no one would be any the wiser, as long as they never saw anything approaching the full resolution image!

Given that both images were shot at 400mm focal length, it’s obvious that the bird in image 1 (now you know it’s cropped a bit) is FURTHER AWAY than the bird in image 2.

So why is one IN FOCUS and the other not?

The bird in image 1 is ‘crossing’ the frame more than it is ‘closing in’ on the camera.

The bird in image 2 is closer to the camera to begin with, and is getting closer by the millisecond.

These two scenarios impose totally different work-loads on the autofocus system.

The ability of the autofocus system to cope with ANY imposed work-load is totally dependent upon the control parameters you have set in the camera.

The ‘success’ rate of these adjustable autofocus parameter settings is effected by:

Changing spatial relationship between camera and subject during a burst of frames.
Subject-to-camera closing speed
Pre-shot tracking time.
Frame rate.

And a few more things besides…!

The autofocus workloads for images 1 & 2 are poles apart, but the control parameter settings are identical.

The Leucistic Red Kite in the shot below is chugging along at roughly the same speed as its non-leucistic cousin in image 2. It’s also at pretty much the same focus distance:

Image 3. Leucistic Red Kite – same distance, closing speed and focal length as image 2. CLICK IMAGE to view larger version.

So why is image 3 IN FOCUS when, given a similar scenario, image 2 is out of focus?

Because the autofocus control parameters are set differently – that’s why.

FACT: no single combination of autofocus control parameter settings will be your ‘magic bullet’ and give you nothing but sharp images with no ‘duds’ – unless you use a 12mm fish-eye lens that is!

Problems and focus errors INCREASE in frequency in direct proportion to increasing focal length.

They will also increase in frequency THE INSTANT you switch from a prime lens to a zoom lens, especially if the ‘zoom ratio’ exceeds 3:1.

Then we have to consider the accuracy and speed of the cameras autofocus system AND the speed of the lens autofocus motor – and sadly these criteria generally become more favourable with an increased price tag.

So if you’re using a Nikon D800 with an 80-400, or a Canon 70D with a 100-400 then there are going to be more than a few bumps in your road. And if you stick to just one set of autofocus control settings all the time then those bumps are going to turn into mountains – some of which are going to kill you off before you make their summit….metaphorically speaking of course!

And God forbid that you try this image 3 ‘head on close up’ malarkey with a Sigma 50-500 – if you want that level of shot quality then you might just as well stay at home and save yourself the hide fees and petrol money !

Things don’t get any easier if you do spend the ‘big bucks’ either.

Fast glass and a pro body ‘speed machine’ will offer you more control adjustments for sure. But that just means more chances to ‘screw things up’ unless you know EXACTLY how your autofocus system works, exactly what all those different controls actually DO, and you know how to relate those controls to what’s happening in front of you.

Whatever lens and camera body combination any of us use, we have to first of all find, then learn to work within it’s ‘effective envelope of operation’ – and by that I mean the REAL one, which is not necessarily always on a par with what the manufacturer might lead you to believe.

Take my Nikon 200-400 for example. If I used autofocus on a static subject, let alone a moving one, at much past 50 metres using the venerable old D3 body and 400mm focal length, things in the critical image sharpness department became somewhat sketchy to say the least. But put it on a D4 or D4S and I can shoot tack sharp focussing targets at 80 to 100 metres all day long……not that I make a habit of this most meaningless of photographic pastimes.

That discrepancy is due to the old D3 autofocus system lacking the ability to accurately discriminate between precise distances from infinity to much over 50 metres when that particular lens was being used. But swap the lens out for a 400 f2.8 prime and things were far better!

Using the lens on either a D4 or D4S on head-on fast moving/closing subjects such as Mr.Leucistic above, we hit another snag at 400mm – once the subject is less than 20 metres away the autofocus system can’t keep up and the image sharpness effectively drops off the proverbial cliff. But zoom out to 200mm and that ‘cut-off’ distance will reduce to 10 metres or so. Subjects closing at slower speeds can get much closer to the camera before sharp focus begins to fail.

As far as I’m concerned this problem is more to do with the speed of the autofocus motor inside the lens than anything else. Nikon brought out an updated version of this lens a few years back – amongst its ‘star qualities’ was a new nano-coating that stopped the lens from flaring. But does it focus any faster – does it heck! And my version doesn’t suffer from flare either….!

Getting to know your equipment and how it all works is critical if you want your photography to improve in terms of image sharpness.

Shameless Plug Number 1.

I keep mentioning it – my ebook on Canon & Nikon Autofocus with long glass.

Understanding Canon & Nikon Autofocus

for

Bird in Flight Photography

Click Image for details.

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Canon 1Dx & 200-400 f4 L IS USM

Posted on March 3, 2015 by Andrew Astbury

A Nikon users thoughts on using the Canon 1Dx and the 200-400 f4L IS USM.

The Canon 200-400 f4 L IS USM on the 1Dx – overall a staggeringly good pairing that I’m really going to miss when I have to give it back!

For years now, my “standard” wildlife photography lens has been the only 200-400f4 that was ever available, the Nikon.

An epic lens; sharp, good resolution in terms of line pairs per millimetre, and most importantly a boon to in-camera composition. It makes an excellent job of everything I ever ask it to do, from cute Red Squirrels 2 metres in front of me, to thumping great Norwegian Sea Eagles barreling towards me at thirty miles per hour and 30 metres out.

However; it’s not without it’s little idiosyncrasies, in fact I often describe it as “a pig” of a lens to use. Sharpness at 50 meters is questionable, and beyond 75 metres is pathetic – the bottom of a milk bottle could do better.

And it hates teleconverters as a rule – yes it’s sharp, but the resolution drops through the floor.

But if you wanted the compositional versatility that only a 200-400 can give you, then you had no option but to shoot Nikon.

Until that is, the day Canon did the unthinkable and launched their version of a 200-400 f4. And they gave it an internally switch-able 1.4x teleconverter giving you an effective 200 f4 to 560 f5.6 working range – WOW!

I first got hold of one of these babies about 4 weeks after they became available; a client at a Drummond Street workshop I was doing for Calumet brought it in stuck on the front of a 1Dx. I’d torn the lens from his poor hands before he knew what was happening, and whipped it outside, stuck the 1Dx in AF case 2, auto iso, 10 frames per second, manual exposure at 1/2000th and f6.3 and began rattling off frames of passing traffic – I was astounded by the lenses performance.

Over the following 18 months I had one or two further opportunities to “have a bash” with the 1Dx + 200- 400 combo, and it honestly impressed the “bejesus” out of me every time; so much so that I’ve recommended any Canon user that asked me to just BUY ONE. And buy one they did!

I’d also had access to a raft of CR2 raw files shot with this combo from one or two other photographers “who know what they are doing”; especially from my old pal Steve “Judith Chalmers” Kaluski of Untamed Images.

As many folk know, I run Eagle Photography workshop tours to Norway every now and again, and with a winter workshop in February 2015 coming up I was thinking that 200mm to 560mm would make this lens perfect for Norway.

Seeing as I “sold” half a dozen of these lenses for Canon I reckoned they owed me a favour – big time.

So I had a word in a few ears at Calumet, and Reece Piper kindly sent me a 1Dx on loan. Canon UK were not quite so forthcoming – basically saying they hadn’t the stock availability to lend me one for upwards of a month. But my favourite Geordie Lass June Lown came to the rescue and volunteered her newly acquired 200-400, bought on the recommendation of yours truly, for the testing and trip to Norway.

So the scene was set for an epic journey into the inner workings of the lens and the 1Dx you have to hang off the back of it in order to get the “best?” out of it.

Testing & Evaluation

Back in the days of yore, when we all shot film, lenses were tested on a full optical test bench, and the MTF charts produced thusly actually meant something. If the lens tested good, but you got soft images you KNEW you had a camera body lens mount problem, or that the pressure plate that held the film in the proper plane was distorted.

But now, certain manufacturers don’t even measure MTF – they use a calculator to work them out based upon theoretical values NOT real ones. And then we have entities like DXO Labs, who test lenses on cameras. This is lunacy if you are wanting to know about TRUE LENS performance, simply because the quality of lens output (the image projected into the sensor plane) is effected by the vagaries of the item that lives there – the sensor!

And on top of that, when testing under non-laboratory conditions, the performance of the lens is further clouded by inaccurate or unsuitable camera settings, especially those pertaining to auto focus.

So field testing of lenses is not simply a case of “point – squirt – evaluate”; it has to be done with more than a modicum of intelligence when it comes to camera AF settings. You have to do TWO things:

1. UNDERSTAND COMPLETELY how the AF system works and what the parameter control adjustments actually do.

2. Evaluate your subjects behaviour in terms of the aforementioned parameters and adjust them accordingly.

You may be interested in acquiring, for a small fee, my pdf guide to Long Lens Autofocus for Canon & Nikon systems.

Previous experience with the 1Dx had led me to treat the camera with a little trepidation for one single reason – its sensor. As a Nikon user I am used to working with sensors which have perhaps the highest Dynamic Range, lowest Base Noise, and highest Signal-to-Noise (S/N) ratios of any popular 35mm format camera body.

On the left is a Canon 1 Dx CR2 file, right is a Nikon D4 NEF file. Both images were shot at identical ISO, aperture, Ev comp and shutter speed within milliseconds of each other on a dual camera rig. The birds cheek patches are “blown” on the CR2, but the highlight detail is all there in the Nikon file.

This is indicative of the shorter Dynamic Range of the 1Dx sensor. The common perception is that the Nikon D4/4s sensors have roughly 1.5 stops greater dynamic range than the Canon 1Dx – this in effect means that the Nikon speed machine can cope with a least DOUBLE the subject brightness range that the 1Dx can handle.

Note: I find enabling Highlight Tone Priority, shooting menu tab 2 setting D+, does NOT sort the problem out in high contrast situations like this – it just gives you problems with the darker tones in the image.

So are there any other “sensor vagaries” on the Canon 1Dx that can effect the overall image quality – you betcha there is…

When I picked the camera up from Calumet I also “accrued” the 100mm f2.8 L macro lens, specifically to test the sensor base noise levels on a studio hi-speed flash shot I wanted to do. I had already done the setup shots the day before on the Nikon D4, as part of my drive to show single-body owners how versatile they can be with their photography.

You can read my article on the 1Dx sensor noise HERE

Canon 1Dx + 100mm f2.8 macro. Nikon SB800 flash & Calumet ProSeries wireless.

The original CR2 file looks like this (left) and the Nikon setup shot is on the right:

But if we open the images in Photoshop and use a standing wave curves layer over the top of them – as we would do when retouching the images – we see the extreme pattern noise in the 1Dx sensor (above), while we have virtually none in the Nikon file.

We can see more clearly the pattern noise in the 1Dx sensor if we view the images at 100% magnification.

Custom Curve layer at 100% – now that pattern noise on the Canon sensor is obvious.

We can derive from this shoot/test that the Canon 1Dx is a bit more “photon-hungry” than your average Nikon pro body sensor, but then doesn’t have the dynamic range capability to cope with lots of photons when it sees them.

Now let’s be real about all this for a moment; the 1Dx sensor is old tech in all fairness to Canon, though I’ll counter that by throwing the venerable Nikon D3 into the argument – that body is older than a 1Dx and has a sensor that performs far better in both dynamic range and base noise departments.

In reality though, the pattern noise, though always present in 1Dx images, is usually hidden or masked by actual image/subject detail so that, for the most part, you don’t see it AT ALL – just don’t try going for low ISO when photographing the “Black Cat in the Coal House at Midnight”, with a 1Dx if you have an aversion to heavy Photoshop work.

As I said before, as a Nikon user, the sensor output of the 1Dx leaves me grimacing a little to say the least. But, climbing back on the fence of neutrality I can see that dedicated Canon users might not notice the problems I see if only on the basis of “what you’ve never had you never miss”.

And as I was to discover, there’s something of a bonus with this sensor that this Nikon user was not expecting…..more later.

The ongoing banter between Nikon and Canon users is all very well, and usually good for a bit of a laugh between fellow photographers BUT, the reality is this – ALL pro level 35mm format camera bodies from either Canon or Nikon have their good points and bad points; and not a single one stands head- and-shoulders above the rest ON ALL COUNTS.

“What the Lord giveth with one hand, he taketh away with the other” is definitely the one saying that springs to my mind when I get asked about cameras! If you know what you are doing it doesn’t matter which one you use, you’ll invariably find 10 things wrong with it in the first 30 minutes!

I don’t like the feel of the 1Dx – it feels like I’m holding a brick – BUT SO WHAT?
I hate the menu system – it’s mental – BUT YOU GET USED TO IT
I dislike the sensor output – BUT IT’S FIXABLE for the most part.
Buttons & button+button or dial combos – COME ON GUYS, I’m neither double jointed or gifted with four hands!

There used to be a very large version of this image on the web that sums up Canon buttons, but I can only find a small version of it now:

Sadly the “Call Spock” button will not work any more – RIP L.N.

My list of gripes and niggles about the 1Dx could go on but, sensor output notwithstanding, that list could be easily matched or exceeded by my list of niggles about Nikon cameras! So expanding on them any further is a pointless exercise.

Likewise, comparing the two 200-400s as separate lenses is a somewhat pointless activity too – they are different beasts by a country mile, and I would liken the task to attempting a comparison between the iconic Z28 Pontiac Firebird and the equally iconic Aston Martin DBS – as I said, pointless.

But I feel justified in comparing certain aspects of the camera bodies, and seeing as I have already dealt with the sensor comparison to a degree, I’ll now look at the other main fundamental difference I see between Canon and Nikon; and that is the autofocus system.

Autofocus:

I am going to make a very broad and sweeping statement now, and that is Canon autofocus is generally better than Nikon autofocus – FACT.

What do I mean by better?

I mean that it is more controllable and furnishes the user with a greater ability to tailor the autofocus to suit the behaviour of the intended subject. But the more eagle-eyed reader will have spotted my use of the word “generally”; that is there to indicate a caveat – and the caveat is this:

Only if you know what you are doing!

If you DON’T, and you start fiddling with settings such Acceleration/Declaration tracking, then you risk getting in a proper old mess and you’ll wish you HAD bought Nikon!

My soon-to-come Autofocus Guide to Nikon and Canon – available from this very boutique – goes into the nitty-gritty of autofocus in great detail – so buy it..

In a nutshell, you can tailor the Canon autofocus system to cope with how the subject moves ALONG the lens axis; that’s where your AF has to do the most work. Is it moving towards the camera at a constant speed, or is it moving towards the camera in a stop-go-slow-fast-slow manner? With the Canon 1Dx AF system you have 5 different settings you can use to cover this manner of movement. And these settings are all independent of your AF point group settings.

On a Nikon you have NO independent way of setting the camera to cope with this aspect of subject movement. Using a nine point group on a Nikon tends to favour subjects that move in a constant direction and speed, while the 21 point group favours the more erratically moving subject; which has always seemed a little silly to me and somewhat short-sighted of Nikon.

After 6 weeks of working with the 1Dx in conjunction with the 200-400mm on all manner of moving subjects in terms of size, speed and proximity to the camera I have come to the conclusion that only Cases 2 & 6 are of any real use to me as a wildlife photographer. But I have a tendency to select Case 3 and modify it in terms of Tracking Sensitivity and Acceleration/Declaration Tracking as a scene/subject presents itself.

The third parameter adjustment – AF Point Switching – for the most part I have tended to leave at the default setting of 0, though a setting of 1 has proved useful when dealing with the more erratically moving subject when you too are moving somewhat erratically, such as being in a small boat at sea.

White-tailed Eagles locking talons – 1Dx + 200-400 hand held from boat, AF Case 6, 9 point AF expansion, AF point switching +1, Manual Exposure, Auto ISO 1/2000th, f6.3 ISO 640

For the sort of work that I do within this focal length range, I would only ever use the AF Area Modes of Spot, Expanded (what I call 1 with 4 friends) and Expanded AF Surround ( 1 with 8 friends). Under NO circumstances do I want to leave the camera to decide on what part of the subject I’m focussing on, so Zone and Auto are off my radar. For the same reason I never use the 3D tracking mode on my Nikons. But having said that, I can very well envisage photographers using much shorter focal lengths benefiting from the other modes in certain circumstances due to the greater inherent depth of field they have at their disposal.

But what impresses me most is the speed of the AF using this camera and lens combination, it makes my D4 and Nikon 200-400 look like a clockwork toy; even though I always thought it was fast enough….

1Dx + 200-400 hand held from boat, AF Case 6, 9 point AF expansion, AF point switching 0, Manual Exposure, Auto ISO 1/2000th, f6.3 ISO 640

I only hit the AF activation on this bird a split second before the shot was taken – razor sharp, see for yourself:

So, I get to this juncture and have to start asking myself a couple of questions:
1. Would this shot, for instance, look even better via a Nikon D4/D4S sensor ?
2. Would I have got this particular shot using the D4 or a D4S and my Nikon 200-400?

The answer to the first question is YES – it would; there would be somewhat less noise for starters, and the extra dynamic range would at least facilitate easier processing. Being so used to NEF files I find I have to do a more delicate balancing act between highlight and shadow tones when processing 1Dx CR2 files.

Using the 1Dx I’m a lot more concious of the fact that I need to “watch” my highlights when shooting, and that when it comes to processing it’s like I’ve gone back to 12bit RAW files – and it’s years since I’ve processed one of those babies!

The answer to question 2 though is a little more problematic. Under the EXACT same circumstances the answer is most likely a NO as it was basically “snap-shot”, and that sort of shooting rarely works out too well on Nikon using an f4 lens when a fast-moving subject is right on top of you.

Using an f2.8 would have pulled this shot off under the same circumstances without a problem.

Had I framed up on this eagle 4 or 5 seconds beforehand and let the AF track it until it got to this position then YES I would have got the same result; as long as I had been in a 21 point group. But I usually don’t favour a 21 point group on Nikon because it’s just that bit harder to be precise – I want focus on the eagles eye and I couldn’t give a you-know-what about its other bits – so I usually opt for a 9 point group.

Bearing in mind that this bird is DECELERATING RAPIDLY, the Nikon 9 point group and its fixed “speed tracking preset” might allow the predictive side of the Nikon AF system to advance the focus a little closer to the camera than needed at the moment the shutter opens; because the “preset” is more geared toward a CONSTANT subject speed.

And seeing that the camera isn’t exactly stable either, being in a small boat, the new Nikon 4 point group might have made an even bigger cock-up because it always attempts to focus on the nearest point – which ISN’T the eagles eye.

It’s all about the Accel/Decel tracking…..(ADT – my acronym!)

On the 1Dx Canon give you 5 totally independent ADT settings, and Nikon give you 2 fixed presets which are enslaved to separate AF point groups.

Shooting large subjects at distance – such as football – makes for light work in terms of ADT and predictive AF due to the inherently large depth of field for any given f-number. But shoot smaller, faster moving subjects at much shorter distances and those same ADT settings will make a huge difference to the focus accuracy of the captured image.

When shooting somewhat slower moving subjects I always like to switch to a single AF point and place it over the subjects eye.

I like the Spot AF setting on the 1Dx for this sort of work, especially when I can get the composition I want using one of the centre diagonal cross-type sensors, as in this Lynx below:

1Dx + 200-400 at 400mm AF Case 2, spot AF, Manual Exposure, Auto ISO 1/250th, f7.1 ISO 1000 IS Pos 2 – just because I could!

1Dx + 200-400 at 400mm AF Case 2, spot AF, Manual Exposure, Auto ISO 1/250th, f7.1 ISO 200 IS Pos 2 – just to see HOW low I could go!

The Arctic Fox above is shot with Spot AF using a conventional cross-type sensor from the centre left column.

The Wolves below are shot with a diagonal cross-type sensor from the centre column placed over the right eye of the wolf in the middle of the shot, but this time I’m in AF point expansion – 1 with 4 friends – with AF point switching set to +1. This covers off any movement of the wolfs eye up, down, left or right and increasing the point switching from 0 to +1 means that the active Af point will switch to one of those “4 friends” in order to follow the eye if I can’t move the camera fast enough:

1Dx + 200-400 at 366mm AF Case 2, single point AF expansion, Manual Exposure, Auto ISO 1/1000th, f7.1 ISO 4000 – I’m being a bit more sensible now – if you call standing taking pictures of this pair of bad boys with nothing twixt me and them except fresh air sensible!

Canon Spot AF uses just the centre portion of the selected AF sensor and so you can do some very precise focussing using this AF mode.

Where I find it a real boon is when working off a tripod or from a hide where the camera is rock steady on some form of gimbal or ball head, as in this type of shot. And it really comes into its own when using the 1.4x built-in TC on the 200-400:

As you can see from the screen-grab below I have a single AF point selected and located exactly where I want it:

What you can’t see is that Spot AF – which I think Canon ought to re-name “precision” – is only using the centre portion (perhaps 50%) of the area marked in red; so the main focus is concentrated where the eagles beak has dug into the side of the Pine Martens head – very cute and cuddly I must say…

Autofocus Conclusion:

Nikon AF is rather “simplified” and to be honest it has served exceptionally well over the years. But the one niggle I’ve always had is that I WANT to dictate what the AF does, and how and when it does it – I loathe and detest being dictated to, especially by some algorithm written by lab tech who wouldn’t know his “arse from his elbow” when it comes to a good picture.

It’s as if those Nikon guys think I’m an idiot and they know best – it’s not true fellas!

In all fairness, they sell cameras to folk who “aspire”, and those folk need some sort of instant gratification. Also, those same folk would not do the sort of photography that I do “as norm” – yes, I AM NIKON; but I am also a minority!

So I can see why Nikon make use of “preset averages” in a lot of their control algorithms – I just wish they made pro versions of their cameras with a lot of these so-thought-of Intelligent functions left out; I for one would certainly be a lot more chilled out of they did.

Canon have always been notorious for crediting their users with more than a modicum of intelligence, yet they still give the “L plate” folk half a chance by offering certain levels of automation and presets.

As someone who uses all the facilities on a camera body close to the boundaries of their design criteria – and sometimes past ’em! – I find the 1Dx AF system fabulous in terms of both speed and tractability, and it negates all the niggles and gripes about the Nikon system that I have soon got to return to….

Unless of course some retailer, or those lovely guys at Canon take pity on me!

A Nikon Users Final Judgement on the 1Dx + 200-400mm f4 L IS USM

For the least 6 weeks I’ve been on something of a journey that’s for sure.

Strange “buttonograhy” has caused me some head-scratching! I’m a back button focus man myself, so no prizes for guessing which button has given me most confusion – that’s right, the STAR BUTTON!

My brain simply cannot retain what its function is, so when I hit it accidentally with a gloved thumb, I’ve developed a really simple remedy for getting rid of it – TURN THE CAMERA OFF then back on again! That’s a proper Andy Pandy fix that is!

When I get into situations where my subjects are moving into and out of the sun, and scene contrast changes constantly, I still adopt my preferred method of shooting, and that is FULL MANUAL with auto ISO.

The venerable Nikon D3 didn’t handle this too well; the ISO was always a “little sticky” at at coming back down to the lower numbers. The D4 is a lot better, but still comes a little unstuck from time to time.

The Canon 1Dx has performed flawlessly and has just come back from 7 days in Norway where it has been permanently in Manual Exposure with Auto ISO from the very first to the very last frame of the trip, and the Auto ISO function has performed perfectly on every frame.

Here is a situation where this method of shooting paid dividends, with one of the most rarely seen raptors on the planet – the Goshawk:

Goshawk in the rain – 1/60th sec, f5.6, Manual Exposure + Auto ISO 12800

We were in the darkest heart of a chunk of Boreal Forest, at dawn, and it was chucking it down with rain – gloomy is not a word that does the lack of light justice.

Like a ghost this male Goshawk materialises in front of us and we need to get the shots. With so little light, and the teleconverter switched in we need to pick the shots off each and every time the bird stops moving its head. So the fastest speed we can use is 1/60th sec, which on a gimbal mounted rig at 560mm is just do-able with good technique.

Slipping the IS into Mode 2 and using Spot AF continually on the Goshawks eye we got a large number of razor sharp images in the poorest light I think I have ever shot in.

Here is a 100% crop from that image:

Now considering that this image is from a sensor that I’m not overly keen on, let’s compare it to a shot on a sensor I’m usually far happier using – that of a D4S, that happened to be about 3 feet to my left and operated by a client, Mr. Paul Atkins, using the Nikon 200-400:

The same 12800 ISO, both these shots are pretty much straight from the sensor with minimal processing.

Well, I know which I prefer, and it isn’t the one done with a black lens!
A lot of folk think 400 ISO is high – well it isn’t; even though it used to be.

As I have said before in this article, the 1Dx sensor – as far as this Nikon user is concerned – is a little short in the performance stakes; but is it?

At more conventional speeds below 3200 ISO I firmly come down on the side of Nikon.

From 3200 ISO to 5000 ISO I don’t think there is much between them, but above 5000 ISO the Canon 1Dx excels by a country mile; and Nikonophilles can argue the toss with me ’til the cows come home – but I have the images to prove it – so “boo-hoo, sucks to you chaps”…

With all DSLRs, as we increase ISO we shorten Dynamic Range, but it would appear that, even though the 1Dx is shorter than a D4S in that department to begin with, it hangs on to it a lot longer – and that means more images you can make money from; or win competitions with, which ever floats your boat.

When the end of the Universe comes and it’s “lights out” for everyone, just make sure you’ve got a 1Dx in your hand – Shutterstock and Getty will rip your arm off for the shots ‘cos they’ll still be around somewhere, and God won’t get rid of them that easy!

Sadly, I’ve got to give the 1Dx back to Calumet so that they can hire it to some un-appreciative plebs and recoup the dough they’ve lost while yours truly has been jollying it up with the Vikings.

And as for the glorious 200-400, well, that’s got to go back to the lovely June Lown who loaned it to me in the first place.

So many thanks to June, and to Reece Piper from Calumet for agreeing to the long loan 1Dx, and to John Willis from Calumet Manchester for knowing everyone, and for “lubricating the gears” that make the world go around.

In closing I suppose I need to answer the question I’ve been asked a lot since word of my Canon-ising escaped into the general UK wildlife scene – am I ditching Nikon?

No is the short answer; not even if I could afford to.
BUT, if I could afford to I WOULD buy a 1Dx and 200-400 f4 L IS USM – today!

I would dump my Nikon 200-400, but keep the D4/D4S for use with a big prime. But given the choice my standard wildlife “go to” lens would be the Canon 200-400 in conjunction with a 1Dx. It would get more shots than it would lose me, and Canon can always get rid of my gripes about the sensor by upgrading it – as long as they don’t lose the superb high ISO performance.

Right, that’s it – I’m off to go curl up in a corner of my office and cry at the thought of giving this gear back to its rightful owners….

I WANT THIS RIG…do I really have to give it back?

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Autofocus Drill-down

Posted on January 31, 2015 by Andrew Astbury

Long Lens Autofocus Considerations.

If you read my previous post about the 1Dx sensor you will have seen that I mentioned my, as yet unfinished, tome about long lens autofocus for wildlife photography. It’s a frustrating project because I keep having to change various bits to make them simpler, re-order certain paragraphs etc.

But I thought I’d blog-post something here that I expand on in the project, and it’s something an awful lot of people NEVER take into consideration.

As a Nikon user I’m used to the vagaries of the Nikon AF system and I manage to work with it just fine – I have to!

But photographers who don’t shoot wildlife, and don’t use 400mm or 500mm lumps of glass as their “standard lens” might not find the vagaries I bitch about quite so apparent; indeed some might not come across them at all.

As a wildlife photographer I shoot in crappy light, I shoot with slow lenses (both in terms of f-number and focus speed), I shoot low contrast subjects on equally low contrast backgrounds, I’m constantly shooting brown-on-brown, grey on grey etc, I shoot stupidly small subjects….the list goes on!

For years, good wildlife photography has been done by pushing camera/lens capabilities beyond their performance design parameters; and this particularly applies to our “expectations” of our latest and greatest AF system – be it Canon or Nikon.

I find so many people who come to my workshops etc. are not even aware of this one simple fact – sharp focus requires more work AND increased speed of work by the lens AF motor the closer a subject is to the camera.

Just try looking at the delineations on the focusing ring of a lens:

Canon 200-400 focused at 20 meters. (Lens porn WARNING: This lens will cause movements in the front-of-trouser department).

Look at the scale and note the distance between 20m and 50m marks – that distance is indicative of the amount of work required of the autofocus controller and motor to move from 20m to 50m or vice versa.

Now look where the 10m mark is – it requires FAR MORE work from the focus controller and motor to move from 20m to 10m, than it did to move the 30 meters from 50m to 20m.

On top of that extra work, if we are tracking a subject moving at 10 meters per second the lens takes 3 seconds to move from 50m to 20m, but then has to move a lot FASTER as well to cover the extra workload moving from 20m to 10m in just 1 second.

Then you wonder why your Nikon D40 + Sigma 50-500mm is crap at doing “birds in flight”; you never realise that your autofocus system is bag of spanners and powered by a hamster on a wheel…….it’s just not fast enough kids

Autofocus accuracy is nothing without speed if you are wanting to do productive wildlife photography.

As I alluded to before, as a photographer of the old wildlife I, and YOU will always encounter problems that users in other photographic disciplines may not, or if they do then the problem has a lot less impact than it does for us.

Think of it this way – a sports photographer will use a 500mm f4 to photograph a 6 foot tall overpaid git who’s 25m to 70m away, on a sunny Saturday afternoon or under a squillion watts of flood lighting; and he’s looking for a 6×12 for the back page of the Sunday Sport. I’ll use the same lens to photograph a cute Red Squirrel at 5m to 7m in a gloomy wood in the middle of winter and I’m looking for a full size, full resolution image for stock.

Red Squirrel – this is basically the FURTHEST DISTANCE you could shoot at with a 500mm lens and still get a meaningful composition. Click for larger view.

Note the distance – 631/100 – that means 6.31 meters. Aperture is f8, so DoF is around 7 centimeters.

The image is UNCROPPED as are all the other images in this post

We don’t really want to be any further away because “his cuteness” will be too small in the frame:

The factors effecting subject distance choice are:

lens resolving power – small, fine details need to be as close as possible.*
sensor resolving power – we need as many pixels as possible covering the subject.*
auto focus point placement accuracy – if the subject is too small in the frame, point placement is inaccurate.
general “in camera” composition

*These two are inextricably intertwined

I’ve indicated the active focus point on the above image too because here’s a depth of field “point of note” – autofocus wastes DoF. Where is the plane of focus? Just between the eyes of the squirrel.

Assuming the accepted modern norm of DoF distribution – 50/50 – that’s 3.5 centimeters in front of the plane of focus, or indicted AF point, that will be sharp. Only problem there is that the squirrel’s nose is only around 1 centimeter closer to the camera than the AF point, so the remaining 2 .5 centimeters of DoF is wasted on a sharp rendition of the fresh air between its nose and the camera!!

Now let’s change camera orientation and go a bit closer to get the very TIGHTEST shot composition:

Red Squirrel – this is basically the CLOSEST DISTANCE you could shoot at with a 500mm lens and still get a meaningful composition. Click for larger view

The subject distance is 5.62 meters. Aperture is f6.3 so DoF is around 4.4 centimeters.

Now let’s change photographic hats and imagine we are a sports photographer and we are spending a Saturday afternoon photographing a bunch of over-paid 6 foot tall gits chasing a ball around a field, using the very same camera and lens:

He’s not over-paid or chasing a ball, but this is the CLOSEST distance we can shoot at with this orientation and still get a “not too tight” composition of a 6 foot git! “Shep’s” not a git really – well, not much! Click to enlarge

The distance for this shot is 29.9 meters. Aperture is f6.3 so DoF is around 1.34 meters.

And here we are at the CLOSEST distance for this horizontal camera orientation – still not too tight. Click to enlarge.

The distance here is 50.1 meters. Aperture is f6.3 so DoF is around 3.79 meters.

So with this new “sports shooter” hat on, have we got an easier job than the cold, wet squirrel photographer?

You bet your sweet life we have!

The “Shepster” can basically jump around and move about like an idiot on acid and stay in sharp focus because:

the depth of field at those distances is large.
more importantly, the autofocus has VERY little work to do along the lens axis, because 1 or 2 meters of subject movement closer to the camera requires very small movements of the lens focus mechanicals.

But the poor wildlife photographer with his cute squirrel has so much more of a hard time getting good sharp shots because:

he/she has got little or no depth of field
small subject movements along the lens axis require very large and very fast movement of the lens focus mechanicals.

So the next time you watch a video by Canon or Nikon demonstrating the effectiveness of their new AF system on some new camera body or other; or you go trawling the internet looking for what AF settings the pros use, just bear in mind that “one mans fruit may be another mans poison” just because he/she photographs bigger subjects at longer average distances”.

Equipment choice and its manner of deployment and use is just not a level playing field is it…but it’s something a lot of folk don’t realise or think about.

And how many folk would ever consider that a desired “in camera” image composition has such a massive set of implications for autofocus performance – not many – but if you put your brain in gear it’s blindingly obvious.

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Exposure Compensation

Posted on July 13, 2014 by Andrew Astbury

Exposure Compensation

Exposure Compensation – that’s something else that cropped up once or twice for the chaps on my recent Norwegian Eagle workshop!

We had something like 420 or more dives from eagles during the trip, and very few if any were shot with flat metering, or 0Ev compensation.

What is Exposure Compensation, and why do we need to use it?

It all begins with this little button:

D3 Exposure Compensation button – Nikon, Canon and most others use the same symbol.

Pushing this button and rotating your main command dial will select a certain exposure compensation value.

Why do we need to use Exposure Compensation though?

Cameras, for all their complexity and “intelligent whotsits” are basically STUPID! They don’t know WHAT you are trying to photograph, or HOW you are trying to photograph it.

They make a lot of very basic assumptions about what you are trying to do – 99.99% of which are WRONG!

The camera does NOT know if you are trying to photograph:

A white cat in a coal shed
A black cat in a snow storm
A white cat in a snow storm
A black cat in a coal shed

All it sees is a frame full of various amounts of light and shade, and depending on your metering mode (which should always be Matrix/Evaluative – see post here) it gives you an “average mean exposure value”.

Take a general scene of fairly low contrast under flat overcast light:

A scene as WE see it.

The same scene as the camera METER sees it.

Lighter tones within the scene.

Some darker area tones within the scene.

The exposure is governed by the PREDOMINANT tone.

As discussed in the previous metering article mentioned earlier, only MATRIX/EVALUATIVE takes the entire frame area into account.

Okay, so that scene was fairly bland on the old tonal front, so let’s have a look at something a little more relevant:

Straight off the camera with no processing. 1/2000th @ f4 1600ISO +1.3Ev

As the camera metered the scene WITHOUT compensation.

Why would the image be so dark and under exposed?

Well here’s an approximation of the cameras average tone “thought process”:

The approximate average value of the scene.

But if we look at some averages WITHIN the overall image:

Random tonal averages within the image.

We can see that the tonal values for the subject are generally darker than the average scene value, therefore the camera records those values as “under exposed”.

This is further compounded by the cameras brain making the decision that the commonest tonal value MUST represent “mid grey” – which it DOESN’T; it’s lighter than that – and so under exposing the image even further!

Now I’m not going to get into the argument about “what is mid grey” and do Nikon et al calibrate to 12%, 18%, 20% or whatever – to be honest it’s “neither here nor there” from our standpoint.

What is CRITICAL though is that we understand the old adage:

“Light Subject Dark Background = Under, or negative exposure compensation. And that Dark Subject Light Background = Over, or positive exposure compensation”.

Okay, but what are we actually doing?

In any exposure mode other than Manual mode, we are allowing the camera to meter the scene AND make the decision over which shutter speed or aperture to use depending on whether we have the camera in Av or Tv mode – that’s Canon-speak for A or S on Nikon.

If we are in shutter priority/S/Tv mode then the camera sets the aperture to give us its metered exposure – that thing that’s usually WRONG! – at the shutter speed we’ve selected.

If, as in the case above, we ADD +1.3Ev – one and one third stops of POSITIVE exposure compensation, the camera uses the shutter speed we’ve selected but then opens up the aperture WIDER than it’s “brain” wants it to.

How wide? 1.3 stops wider, thus allowing 1.3 stops more light into the the sensor during the exposure time.

If we were in Av/A or aperture priority mode then it’s the shutter speed that would take up the slack and become 1.3 stops SLOWER than the cameras “brain” wanted it to be.

Here’s an example of negative exposure compensation:

1/3200th @ f4.5 1000ISO -1.3Ev exposure compensation.

In this particular shot we’re pointing towards the sun – a “dark subject, light background” positive exposure compensation scenario, or so you’d think.

But I want to “protect” those orange highlights in the water and the brightest tones in the eagle, so if I “peg those highlights” just over a stop below the top end of the cameras’ tonal response curve then there is no way on earth they are going to “blow” in the final RAW file.

Manual Exposure mode can still furnish us with exposure compensation based on metering if we engage AUTO-ISO. If we decide we want to shoot continuously with a high shutter speed and a set aperture at a fixed ISO then our exposures are going to be all over the place. But if we engage AUTO-ISO and let the camera choose the ISO speed via the meter reading, we can use the exposure compensation adjustments just the same as we do in Av or Tv modes.

This get’s us away from the problem of fixed ISO Tv mode running out of aperture in low light or when very high shutter speeds are needed; or conversely, stopping the aperture down too far when the sun comes out! – I’ll do a breakdown on this method of shooting later in the year – it’s not without it’s problems.

Next time you get the chance to stand by a large lake or other body of water, just take a moment to notice that the water is dark in some places and light in others. ambient light falling on a moving subject can easily be very uniform and so the subject basically has the same exposure value all the time. But it’s the changing brightness of the background as the subject moves across it that causes us to need exposure compensation.

People seem to think there’s some sort of “magic” at play when they come out with me and I’m throwing exposure compensation values at them. But there’s no magic here folks, just an ability to see beyond “the subject, framing etc” and to actually “see the light” and understand it.

After all, when we click our shutters we are imaging light – the subject is, for the most part, purely incidental!

And there’s only one way you can learn to see light and grasp its implications for camera exposure, and that’s to practice.

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Auto Focus Work Out

Posted on July 1, 2014 by Andrew Astbury

Auto Focus Work Out

My recent summer trip to Flatanger in Norway, and to the famous “Eagle Man of Norway” Ole Martin Dahle, proved, as ever, a severe test of the auto focus capabilities of the gear!

We had 4 guys on the trip, 3 Nikon and 1 Canon, and White-tailed Eagles doing more than 40mph and turning on a dime is one of the hardest tests for auto focus tracking and lock on that you can imagine – especially when it’s all done hand held from a boat that’s rolling around in the sea swell.

wildlife photography,auto focus,Nikon,D4,Andy Astbury,eagle,Norway,workshop,camera settings

The Guys – yours truly, Malcolm Clayton and Paul Atkins; and Mohamed El Ashkar (all the way from Cairo!) and our Cambridge “Don” – all trips should have one – Jamie Gundry. Photo by Ole Martin Dahle.

We had a conglomeration of D4’s, D800E’s and 200-400 f4’s, with a smattering of 300mm and 400mm f2.8’s – and then there was Mohamed with his solitary 1Dx and 300 f2.8.

And our target:

Say “Hello” to “Brutus” – an eagle who lives up to his name for sure – a total brute, especially to a boat full of daft photographers! CLICK for larger view.

Just to set the scene with regard to the technical side of things; birds fly into the wind given the choice, and the sun is wherever it decides to be! So the boat driver – Ole – always needs to position the boat so that “wind and sunlight” are coming from pretty much the same direction, otherwise the birds are not front-lit and cast their own shadows across themselves. In other words the images look like crap!

Some birds come towards the boat, take the fish and then turn away; some will do their approach parallel to the boat; and gits like Brutus will fly low and fast straight at you, pick the fish and then turn straight for the boat and climb.

But no matter how they choose to approach the camera boat all the birds pick the fish and go back to where they’ve come from.

Ole has intimate knowledge of these birds as individuals, and so has a damn good idea of what they will do as they come to the boat. This enables him to manoeuvre the boat for the best shots, and this skill is what you pay for.

Perhaps by now you’ve got the general feel for the situation – a boat that’s subject to wave motion and which might suddenly go backwards 10 yards through its own wake – not the steadiest of camera platforms!

Couple that with trying to make the auto focus lock on and track the bird, and maintain a modicum of composition – it’s just damned hard work.

Photographing anything that’s moving is hard work; moving erratically is even harder; and hand holding on an oscillating camera platform makes the job beyond hard. This style of shooting will NEVER yield vast rafts of sharp sequential images – anyone who tells you different is an outright liar. Christ, even licensed FIA F1 ‘togs are on “easy street” by comparison.

Auto focus cannot be set up perfectly for this sort of situation, but understanding it is a MUST if you want to maximise the opportunity.

Auto Focus Choices

There are 3 main things that control the effectiveness of auto focus and AF tracking:

AF Area Mode

AF Tracking Lock-on interval

Frame Rate

(Bare in mind I’m talking Nikon here, but sorting Mohameds’ 1Dx out showed my that Canon AF is pretty much the same).

Now I dealt with the latter in a previous post HERE and so we need to concentrate here on AF area modes in the main.

Let’s look at what we have to work with on a Nikon body – in this case a D4:

Firstly, the AF sensor layout.

All 51 focus sensors, and there approximate layout in relation to the image frame:

All 51 of the Nikon Multi Cam 3500 FX focus sensors – both cross and linear sensors depicted.

Just the Cross-type Sensors:

wildlife photography,auto focus,Nikon,D4,Andy Astbury,eagle,Norway,workshop,camera settings,Nikon Multi-Cam 3500 FX unit

The 15 Cross type focus sensors on the Nikon Multi-Cam 3500 FX unit.

The Linear-type Sensors:

The 36 Linear type focus sensors on the Nikon Multi-Cam 3500 FX unit.

Single Area AF

Single Area, or single point AF.

9 Point Dynamic Area AF:

9 Point Dynamic Area AF

9 Point DA AF as displayed in the viewfinder (drop shadows added in Photoshop behind the dots to aid visibility in this article).

21 Point Dynamic Area AF:

21 Point Dynamic Area AF

21 Point DA AF as displayed in the viewfinder (drop shadows added in Photoshop behind the dots to aid visibility in this article).

51 Point Dynamic Area AF:

51 Point DA AF as displayed in the viewfinder (drop shadows added in Photoshop behind the dots to aid visibility in this article).

As a stills photographer you are using what’s called Phase Detection auto focus (that’ll be another blog post topic!) but it still relies on a mix of contrast,luminosity and colour to work out what it should be concentrating on in the frame.

Consider the following 2 images, A & B:

A. Dark Subject and Light Background.
Subject itself is low contrast, background water is higher contrast. Subject is at 15 meters, Focal Length is 240mm

B. Light Subject against a Dark Background.
Subject now has a slightly higher contrast, and background is lower contrast. Subject 29 meters, Focal length 360mm

Auto focus is dumb; just plain stupid, left to its own devices. It, like me (yep, me dumb too!) favours lighter things with a higher degree of contrast. The lighter something is then the brighter and more saturated it colour is, and this in turn gives it higher localised contrast.

Auto focus will be happier locking on to and tracking Eagle B than Eagle A.

In A, the AF will want to switch to the lighter, more contrasty water behind the bird – unless of course you “hobble it” and stop it from doing so…

And you stop it by BLINDING IT – in other words use LESS active auto focus points!

“If it ain’t got ’em it can’t switch to ’em!”

If all the AF points in use are on the important part of the subject (the EYE in this case) then there’s little or no chance of the auto focus switching to somewhere you don’t want it to go to.

In a perfect world we’d all be using Single Area AF on a tripod and panning away quite happily keeping that single sensor on the targets eye……………oh I wish!!!!!!

51 point AF is out for this sort of work – with what I’ve just written you should now easily understand why.

So we are down to either the 9 point or 21 point Dynamic Areas.

It all comes down to two things:

How steady you can keep the camera.
How big in the frame the birds are – in other words, subject distance.

But accuracy of auto focus will always be improved by using the least number of sensors you can get away with.

Image A. is at 240mm and a subject distance of 15 meters, and Image B. is at 360mm and a subject distance of 29 meters. Both images were shot using 21 point Dynamic Area AF, 1/2000th @ f7 and 1600ISO.

21 point AF, 15 meters and 240mm focal length.

21 point AF, 29 meters and 360mm focal length.

On the upper detail image there’s one, perhaps two of the 21 sensors that are NOT on the subject.

On the second image there are at least 9 sensors out of the 21 in the group that are NOT on the bird.

If the bird in image A. had been 29 meters away I’ll guarantee it would have been out of focus – why?

Lack of good directional light.
Poor subject contrast and illumination.
Brighter, higher contrast background.
More sensors “Off Target”.

And the auto focus hasn’t wanted to wander to the background on image B. because there’s nothing there for it to favour over the main subject.

How Dynamic Area AF Works

9 point DA auto focus uses the single AF point that you select, but activates the 8 points surrounding it. If you, or the subject, or both, move so that the single point you selected comes “off target” then one of those 8 surrounding points will “cover” the error and maintain focus lock and tracking until you get back on target.

In 9 point DA, auto focus ALL the sensors activated are “cross type” sensors, assuming you use a sensor on the vertical center line of the AF grid.

In 21 point DA, auto focus is still centered on the single sensor you select, but now the surrounding 20 are activated. But at least 6 of these sensors will be linear, not cross type sensors.

Auto Focus Senor Types – Cross and Linear (line).

This is going to be immensely paraphrased!

AF sensors need to see edge detail in order to work. A linear sensor can work more effectively when the edge it’s looking at is perpendicular to it.

The more an edge is parallel to said line sensor then the harder time it has in discerning when said edge is sharp or not.

But if we add 2 line sensors together at right angles to each other, then an edge that is parallel to one line is perpendicular to the other – so edge detection is greatly enhanced.

In an ideal scenario 9 point Dynamic Area AF, centered in the middle of the view finder and kept on the eagles head would be the ideal way to go, but with the other circumstances of:

Moving camera platform
Potential closeness of subject (sub 15 meters possible)

then 9 point DA might be a wee bit tight on both counts, and 21 point makes more sense from a tracking and shooting perspective.

But it leads to an initial problem with the auto focus acquiring the target in the first place. You have to pick these eagles up quite a way out, and if one is coming low to the water then there is possibly too much in the frame to act as a distraction to the auto focus unit itself; though this isn’t quite such an issue if the bird is high in the sky.

So my recommendation for any form of bird-in-flight photography is to start out at 9 point DA and see how you get on!

There is always the AF Tracking Lock On feature that you can deploy in order to “hobble” the AF unit from switching to subjects closer to or further away, but if I’m honest I find this the most sticky and difficult aspect of the Nikon system to get a precise handle on. It does exactly “what it says on the tin” but it’s the “when” and “how much by” bits that have me slightly guessing.

Sometimes I put it on long and it basically waits for perhaps 4 or 5 seconds before it tries to switch focus, while at other times it does so in less than half the time. Sometimes I feel it actually diminishes the effectiveness of the “predictive” side of the auto focus tracking unit.

But if I turn it off when hand holding the camera for flight shots then everything turns to crap – so I turn it back on again!

Again, my base recommendations for this are SHORT to NORMAL and see how things go.

One thing that can have a considerable impact on the way you perceive your auto focus effectiveness is how you have your AF release priority set up (CS a1).

There are 4 options:

Release
Focus+Release
Release+Focus
Focus

By default this is set to FOCUS. With the default setting, it’s theoretically impossible to take a soft shot. But in practice that’s not so simple, and I’ve taken many a soft shot when the D4 “thinks” things are sharp; though in the main, that seems to have been cured the minute we got trap focus back with the latest firmware upgrade.

Release means the camera will take shots irrespective of focus being acquired or not. I NEVER use this option.

Focus+Release means that the first frame will only be taken once focus is acquired, and subsequent frames will be taken irrespective of focus. This is one of my preferred options when everything is unstable – that first frame hopefully sets up the auto focus and AF tracking and so everything SHOULD keep the subsequent frames sharp – please note the use of the word “should”!

Both the above release priority modes do NOT slow the frame rate.

Release+Focus – works the opposite way to Focus+Release – it does slow the frame rate down giving the mirror more down-time and so the auto focus system has more time to work. This is my other preferred option, the one I use when the “action” may not be as repeatable.

Focus – This is the option I deploy when shooting from a tripod or when the action is not quite so fast-paced. Again, this option slows the frame rate.

The Back Button Auto Focus Option

I always use the back button for auto focus activation. There are plenty of arguments for doing this, but I just feel it’s darn right more efficient than having AF activation on the shutter button. Just don’t forget to turn AF/Shutter ON to OFF in the menu, otherwise you are just wasting time and effort!

Conclusion

A lot of folk feel that their auto focus is flawed; but more often it is they and their setup choices which are flawed.

There is no blanket panacea or magic bullet setting for your AF system – as with everything else you have to constantly evaluate the light around you, anticipate the shot and make the necessary changes to setup – otherwise it’s going to be a sad day.

But knowing how your gear works and how it reacts under different scenarios is the “meat and two veg” of good photography. Couple that with shot anticipation and the proper corrective measures and it’s off home for tea and medals!

But above all, remember to have a laugh – you’re a long time dead……..

“GIMME SOME, YOU MEAN BARSTARD!”

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What Shutter Speed?

Posted on March 17, 2014 by Andrew Astbury

Shutter speed, and the choices we make over it, can have a profound effect on the outcome of the final image.

Now everyone has a grasp of shutter speed and how it relates to subject movement – at least I hope they do!

We can either use a fast shutter speed to freeze constant action, or we can use a slow shutter speed to:

Allow us to capture movement of the subject for creative purposes
Allow us to use a lower ISO/smaller aperture when shooting a subject with little or no movement.

Fast Shutter Speed – I need MORE LIGHT Barry!

shutter speed,Red Kite,Andy Astbury,action photography,Wildlife in Pixels

1/8000th sec @ f8, Nikon D4 and 500mm f4

Good strongish sunlight directly behind the camera floods this Red Kite with light when it rolls over into a dive. I’m daft enough to be doing this session with a 500mm f4 that has very little in the way of natural depth-of-field so I opt to shoot at f8. Normally I’d expect to be shooting the D4 at 2000iso for action like this but my top end shutter speed is 1/8000th and this shutter speed at f8 was slightly too hot on the exposure front, so I knocked the ISO down to 1600 just to protect the highlights a little more.

Creative Slow Shutter Speed – getting rid of light.

1/5th sec @ f22

I wanted to capture the movement in a flock of seagulls taking off from the water, so now I have to think the opposite way to the Kite shot above.

Firstly I need to think carefully about the length of shutter speed I choose: too short and I won’t capture enough movement; and too long will bring a vertical movement component into the image from me not being able to hold the camera still – so I opt for 1/5th sec.

Next to consider is aperture. Diffraction on a deliberate motion blur has little impact, but believe it or not focus and depth of field DO – go figure!

So I can run the lens at f16/20/22 without much of a worry, and 100 ISO gets me the 1/5th sec shutter speed I need at f22.

Slow Shutter Rear Curtain Synch Flash

We can use a combination of both techniques in one SINGLE exposure with the employment of flash, rear curtain synch and a relatively slow shutter speed:

6/10th sec @ f3.5 -1Ev rear curtain synch flash

A technique the “Man Cub” uses to great effect in his nightclub photography, here he’s rotated the camera whilst the shutter is open, thus capturing the glowing LEDs and other highlights as circular trails. As the shutter begins to close, the scene is lit by the 1/10,000th sec burst of light from the reduced power, rear curtain synched SB800 flash unit.

But things are not always quite so cut-and-dried – are they ever?

Assuming the lens you use is tack sharp and the subject is perfectly focused there are two factors that have a direct influence upon how sharp the shot will be:

System Vibration – caused by internal vibrations, most notably from the mirror being activated.
Camera Shake – caused by external forces like wind, ground vibration or you not holding the camera properly.

Shutter Speed and System Vibration

There was a time when we operated on the old adage that the slowest shutter speed you needed for general hand held shooting was equal to 1/focal length.

So if you were using a 200mm lens you shot with a minimum shutter speed of 1/200th sec, and, for the most part, that rule served us all rather well with 35mm film; assuming of course that 1/200th sec was sufficient to freeze the action!

Now this is a somewhat optimistic rule and assumes that you are hand holding the camera using a good average technique. But put the camera on a tripod and trigger it with a cable or remote release, and it’s a whole new story.

Why? Because sticking the camera on a tripod and not touching it during the exposure means that we have taken away the “grounding effect” of our mass from the camera and lens; thus leaving the door open to for system vibration to ruin our image.

How Does System Vibration Effect an Image?

Nowadays we live in a digital world with very high resolution sensors instead of film. and the very nature of a sensor – its pixel structure (to use a common parlance) has a direct influence on minimum shutter speed.

So many camera owners today have the misguided notion that using a tripod is the answer to all their prayers in terms of getting sharp images – sadly this ain’t necessarily so.

They also have the other misguided notion that “more megapixels” makes life easier – well, that definitely isn’t true!

The smallest detail that can be recorded by a sensor is a point of light in the projected image that has the same dimensions a one photosite/pixel on that sensor. So, even if a point is SMALLER than the photosite it strikes, its intensity or luminance will effect the whole photosite.

shutter speed,Red Kite,Andy Astbury,action photography,Wildlife in Pixels,vibration reduction,camera shake,mirror slap,sharp images.

A point of light smaller than 1 photosite (left) has an effect on the whole photosite (right).

If the lens is capable of resolving this tiny detail, our sensor – in this case (right) – isn’t, and so the lens out-resolves the sensor.

But let’s now consider this tiny point detail and how it effects a sensor of higher resolution; in other words, a sensor with smaller photosites:

The same detail projected onto a higher resolution sensor (right). Though not shown, the entire photosite will be effected, but its surface area represents a much small percentage of the whole sensor area – the sensor now matches the lens resolution.

Now this might seem like a good thing; after all, we can resolve smaller details. But, there’s a catch when it comes to vibration:

A certain level of vibration causes the small point of light to vibrate. The extremes of this vibration are represented by the the outline circles.

The degree of movement/vibration/oscillation is identical on both sensors; but the resulting effect on the exposure is totally different:

The same level of vibration has more effect on the higher resolution sensor.

If you read the earlier post on sensor resolution and diffraction HERE you’ll soon identify the same concept.

The upshot of it all is that “X” level of internal system vibration has a greater effect on a higher resolution sensor than it does on a lower resolution sensor.

Now what’s all this got to with shutter speed I hear you ask. Well, whereas 1/focal length used to work pretty well back in the day, we need to advance the theory a little.

Let’s look at four shots from a Nikon D3, shot with a 300mm f2.8, mounted on a tripod and activated by a remote (so no finger-jabbing on the shutter button to effect the images).

Also please note that the lens is MANUALLY FOCUSED just once, so is sharply on the same place for all 4 shots.

These images are full resolution crops, I strongly recommend that you click on all four images to open them in new tabs and view them sequentially.

Shutter = 1/1x (1/320th) Focal Length. No VR, No MLU (Mirror Lock Up). Camera on Tripod+remote release.

Shutter = 1/2x (1/640th) Focal length. No VR. No MLU. Camera on Tripod+remote release.

Shutter = 1/2x Focal length + VR. No MLU. Camera on Tripod+remote release.

Shutter = 1/2x Focal length. Camera on Tripod+remote release + MLU – NO VR + Sandbag.

Now the thing is, the first shot at 1/320th looks crap because it’s riddled with system vibration – mainly a result of what’s termed ‘mirror slap’. These vibrations travel up the lens barrel and are then reflected back by the front of the lens. You basically end up with a packet of vibrations running up and down the lens barrel until they eventually die out.

These vibrations in effect make the sensor and the image being projected onto it ‘buzz, shimmy and shake’ – thus we get a fuzzy image; and all the fuzziness is down to internal system vibration.

We would actually have got a sharper shot hand holding the lens – the act of hand holding kills the vibrations!

As you can see in shot 2 we get a big jump in vibration reduction just by cranking the shutter speed up to 2x focal length (actually 1/640th).

The shot would be even sharper at 3x or 4x, because the vibrations are of a set frequency and thus speed of travel, and the faster the shutter speed we use the sooner we can get the exposure over and done with before the vibrations have any effect on the image.

We can employ ‘mirror up shooting’ as a technique to combat these vibrations; by lifting the mirror and then pausing to give the vibrations time to decay; and we could engage the lens VR too, as with the 3rd shot. Collectively there has been another significant jump in overall sharpness of shot 3; though frankly the VR contribution is minimal.

I’m not a very big fan of VR !

In shot 4 you might get some idea why I’m no fan of VR. Everything is the same as shot 3 except that the VR is OFF, and we’ve added a 3lb sandbag on top of the lens. This does the same job as hand holding the lens – it kills the vibrations stone dead.

When you are shooting landscapes with much longer exposures/shutter speeds THE ONLY way to work is tripod plus mirror up shooting AND if you can stand to carry the weight, a good heavy sand bag!

Shot 4 would have been just as sharp if the shutter had been open for 20 seconds, just as long as there was no movement at all in the subject AND there was no ground vibration from a passing heavy goods train (there’s a rail track between the camera and the subject!).

For general tripod shooting of fairly static subjects I was always confident of sharp shots on the D3 (12Mb) at 2x focal length.

But since moving to a 16Mp D4 I’ve now found that sometimes this let’s me down, and that 2.5x focal length is a safer minimum to use.

But that’s nothing compared to what some medium format shooters have told me; where they can still detect the effects of vibration on super high resolution backs such as the IQ180 etc at as much as 5x focal length – and that’s with wide angle landscape style lenses!

So, overall my advice is to ALWAYS push for the highest shutter speed you can possibly obtain from the lighting conditions available.

Where this isn’t possible you really do need to perfect the skill of hand holding – once mastered you’ll be amazed at just how slow a shutter speed you can use WITHOUT employing the VR system (VR/IS often causes far more problems than it would apparently solve).

For long lens shooters the technique of killing vibration at low shutter speeds when the gear is mounted on a tripod is CRITICAL, because without it, the images will suffer just because of the tripod!

The remedy is simple – it’s what your left arm is for.

So, to recap:

If you shot without a tripod, the physical act of hand holding – properly – has a tendency to negate internal system vibrations caused by mirror slap etc just because your physical mass is in direct contact with the camera and lens, and so “damps” the vibrations.
If you shoot without a tripod you need to ensure that you are using a shutter speed fast enough to negate camera shake.
If you shoot without a tripod you need to ensure that you are using a shutter speed fast enough to FREEZE the action/movement of your subject.

Camera Shake and STUPID VR!

Now I’m going to have to say at the outset that this is only my opinion, and that this is pointed at Nikons VR system, and I don’t strictly know if Canons IS system works on the same math.

And this is not relevant to sensor-based stabilization, only the ‘in the lens’ type of VR.

The mechanics of how it works are somewhat irrelevant, but what is important is its working methodology.

Nikon VR works at a frequency of 1000Hz.

What is a “hertz”? Well 1Hz = 1 full frequency cycle per second. So 1000Hz = 1000 cycles per second, and each cycle is 1/1000th sec in duration.

Full cycle sine wave showing 1,0.5 & 0.25 cycles.

Now then, here’s the thing. The VR unit is measuring the angular momentum of the lens movement at a rate of 1000 times per second. So in other words it is “sampling” movement every 1/1000th of a second and attempting to compensate for that movement.

But Nyquist-Shannon sampling theory – if you’re up for some mind-warping click HERE – says that effective sampling can only be achieved at half the working frequency – 500 cycles per second.

What is the time duration of one cycle at a frequency of 500Hz? That’s right – 1/500th sec.

So basically, for normal photography, VR ceases to be of any real use at any shutter speed faster than 1/500th.

Remember shot 3 with the 300mm f2.8 earlier – I said the VR contribution at 1/640th was minimal? Now you know why I said it!

Looking again at the frequency diagram above, we may get a fairly useful sample at 1/4 working frequency – 1/250th sec; but other than that my personal feelings about VR is that it’s junk – under normal circumstances it should be turned OFF.

What circumstances do I class as abnormal? Sitting on the floor of a heli doing ariel shots out of the open door springs to mind.

If you are working in an environment where something is vibrating YOU while you hand hold the camera then VR comes into its own.

But if it’s YOU doing the vibrating/shaking then it’s not going to help you very much in reality.

Yes, it looks good when you try it in the shop, and the sales twat tells you it’ll buy you three extra stops in shutter speed so now you can get shake-free shots at 1/10th of a second.

But unless you are photographing an anaesthetized Sloth or a statue, that 1/10th sec shutter speed is about as much use to you as a hole in the head. VR/IS only stabilizes the lens image – it doesn’t freeze time and stop a bird from flapping its wings, or indeed a brides veil from billowing in the breeze.

Don’t get me wrong; I’m not saying VR/IS is a total waste of time in ALL circumstances. But I am saying that it’s a tool that should only be deployed when you need it, and YOU need to understand WHEN that time is; AND you need to be aware that it can cause major image problems if you use it in the wrong situation.

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In Conclusion

1/2000th sec is sufficient to pretty much freeze the forward motion of this eagle, but not the downward motion of the primary feathers.

This rather crappy shot of a White-tailed eagle might give you food for thought, especially if compared with the Red Kite at the start of the post.

The primary feathers are soft because we’ve run out of depth of field. But, notice the motion blur on them too? Even though 1/2000th sec in conjunction with a good panning technique is ample to freeze the forward motion of the bird, that same 1/2000th sec is NOT fast enough to freeze the speed of the descending primary feathers on the end of that 4 foot lever called a wing.

Even though your subject as a whole might be still for 1/60th sec or longer, unless it’s dead, some small part of it will move. The larger the subject is in the frame then more apparent that movement will be.

Getting good sharp shots without motion blur in part of the subject, or camera shake and system vibration screwing up the entire image is easy; as long as you understand the basics – and your best tool to help you on your way is SHUTTER SPEED.

A tack sharp shot without blur but full of high iso noise is vastly superior to a noiseless shot full of blur and vibration artefacting.

Unless it’s done deliberately of course – “H-arty Farty” as my mate Ole Martin Dahle calls it!

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Metering Modes Explained

Posted on February 27, 2014 by Andrew Astbury

Camera Metering Modes

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I always get asked about which camera metering mode I use, and to be honest, I think sometimes the folk doing the asking just can’t get their heads around my simplistic, and sometimes quite brutal answers!

“Andy, it’s got to be more complicated than that surely….otherwise why does the camera give me so many options…?”

Well, I always like to keep things really simple, mainly because I’m not the brightest diamond in the jewellery shop, and because I’m getting old and most often times my memory keeps buggering off on holiday without telling me!

But before I espouse on “metering the Uncle Andy way” let’s take a quick look at exactly how the usual metering options work and their effects on exposure.

The Metering Modes

Average (a setting usually buried in the center-weighted menu)
Spot
Center-weighted
3D Matrix (Nikon) or Evaluative (Canon)

Metering Mode Icons

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Auto Focus & Shooting Speed

Posted on February 24, 2014 by Andrew Astbury

Auto Focus & Shooting Speed

Firstly, an apology to my blog followers for the weird blog post notification this morning – I had one of those “senior moments” where I confused the Preview button with Publish – DOH!

There is truly no hope………..! But let’s get on….

The effectiveness of auto focus and its ability to track and follow a moving subject IS INFLUENCED by frame rate.

Why is this I here you ask.

Well, it’s simple, and logical if you think about it – where are your AF sensors?

They’re in the bottom of your cameras mirror box.

Most folk thing that the mirror just sits there, reflecting at 45 degrees all the light that comes through the lens up to the focus screen and viewfinder. The fact that the mirror is still DOWN when they are using the auto focus leads most people into thinking the AF sensor array is elsewhere – that’s if they can be bothered to think about it in the first place.

So how does the AF array SEE the scene?

Because the center area of the main mirror is only SEMI silvered, and in reality light from the lens does actually pass through it.

auto focus,how auto focus works,main mirror,dslr mirror,mirror box,photography,camera

Main mirror of a Nikon D2Xs in the down position.

Now I don’t recommend you jam a ball point pen under your own main mirror, but in the next image:

Main mirror of a Nikon D2Xs lifted so you can see the secondary mirror.

Now there’s a really good diagram of the mechanics at http://www.reikan.co.uk/ – makers of FoCal software, and I’ll perhaps get my goolies cut of for linking to it, but here it is:

This image belongs to Reikan

As you can now hopefully understand, light passes through the mirror and is reflected downwards by the secondary mirror into the AF sensor array.

As long as the mirror is DOWN the auto focus sensor array can see – and so do its job.

Unless the MAIN mirror is fully down, the secondary mirror is not in the correct position to send light to the auto focus sensor array – SO GUESS WHAT – that’s right, your AF ain’t working; or at least it’s just guessing.

So how do we go about giving the main mirror more “down time”? Simply by slowing the frame rate down is how!

When I’m shooting wildlife using a continuous auto focus mode then I tend to shot at 5 frames per second in Continuous LOW (Nikon-speak) and have the Continuous HIGH setting in reserve set for 9 frames per second.

The Scenario Forces Auto Focus Settings Choices

From a photography perspective we are mainly concerned with subjects CROSSING or subjects CLOSING our camera position.

Once focus is acquired on a CROSSING subject (one that’s not changing its distance from the camera) then I might elect to use a faster frame rate as mirror-down-time isn’t so critical.

But subjects that are either CLOSING or CROSSING & CLOSING are far more common; and head on CLOSING subjects are the ones that give our auto focus systems the hardest workout – and show the system failures and short-comings the most.

Consider the focus scale on any lens you happen to have handy – as you focus closer to you the scale divisions get further apart; in other words the lens focus unit has to move further to change from say 10 meters to 5 meters than it does to move from 15 meters to 10 meters – it’s a non-linear scale of change.

So the closer a subject comes to your camera position the greater is the need for the auto focus sensors to see the subject AND react to its changed position – and yes, by the time it’s acquired focus and is ready to take the next frame the subject is now even closer – and things get very messy!

That’s why high grade dSLR auto focus systems have ‘predictive algorithms’ built into them.

Also. the amount of light on the scene AND the contrast between subject and background ALL effect the ability of the auto focus to do its job. Even though most pro-summer and all pro body systems use phase detection auto focus, contrast between the subject to be tracked and its background does impact the efficiency of the overall system.

A swan against a dark background is a lot easier on the auto focus system than a panther in the jungle or a white-tailed eagle against a towering granite cliff in Norway, but the AF system in most cameras is perfectly capable of acquiring, locking on and tracking any of the above subjects.

So as a basic rule of thumb the more CLOSING a subject is then the LOWER your frame rate needs to be if you are looking for a sharp sequence of shots. Conversely the more CROSSING a subject is then the higher the frame rate can be and you might still get away with it.

Points to Clarify

The mechanical actions of an exposure are:

Mirror lifts
Front shutter curtain falls
Rear shutter curtain falls
Mirror falls closed (down)

Here’s the thing; the individual time taken for each of these actions is the same ALL the time – irrespective of whether the shutter speed is 1/8000th sec or 8 sec; it’s the gap in between 2. & 3. that makes the difference.

And it’s the ONLY thing shutter-related we’ve got any control over.

So one full exposure takes t1 + t2 + shutter speed + t3 +t4, and the gap between t4 and the repeat of t1 on the next frame is what gives us our mirror down time between shots for any given frame rate. So it’s this time gap between t4 and the repeat of t1 that we lengthen by dropping the shooting speed frame rate.

There’s another problem with using 10 or 11 frames per second with Nikon D3/D4 bodies.

10 fps on a D3 LOCKS the exposure to the values/settings of the first frame in the burst.

11 fps on a D3 LOCKS both exposure AND auto focus to the values/settings of the first frame in the burst.

11 fps on a D4 LOCKS both exposure AND auto focus* to those of the first frame in the burst – and it’s one heck of a burst to shoot where all the shots can be out of focus (and badly exposed) except the first one!

*Page 112 of the D4 manual says that at 11fps the second and subsequent shots in a burst may not be in focus or exposed correctly.

That’s Nikon-speak for “If you are photographing a statue or a parked car ALL your shots will be sharp and exposed the same; but don’t try shooting anything that’s getting closer to the camera, and don’t try shooting things where the frame exposure value changes”.

There’s a really cool video of 11 fps slowed right down with 5000fps slo-mo HERE but for Christ’ sake turn your volume down because the ST is some Marlene Dietrich wannabe!

So if you want to shoot action sequences that are sharp from the first frame to the last then remember – DON’T be greedy – SLOW DOWN!

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Raw File Compression.

In Conclusion

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Image Sharpness

Shameless Plug Number 1.

Understanding Canon & Nikon Autofocus

for

Bird in Flight Photography

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Testing & Evaluation

Autofocus:

Autofocus Conclusion:

A Nikon Users Final Judgement on the 1Dx + 200-400mm f4 L IS USM

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Long Lens Autofocus Considerations.

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Exposure Compensation

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Auto Focus Work Out

Auto Focus Choices

How Dynamic Area AF Works

Auto Focus Senor Types – Cross and Linear (line).

The Back Button Auto Focus Option

Conclusion

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Fast Shutter Speed – I need MORE LIGHT Barry!

Creative Slow Shutter Speed – getting rid of light.

Slow Shutter Rear Curtain Synch Flash

Shutter Speed and System Vibration

How Does System Vibration Effect an Image?

Camera Shake and STUPID VR!

In Conclusion

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Camera Metering Modes

The Metering Modes

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Auto Focus & Shooting Speed

The Scenario Forces Auto Focus Settings Choices

Points to Clarify

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