Tag Archives: autofocus

Nikon Z7 – I am a Bad Idea

Posted on by
Reply

Nikon Z7 – I am a Bad Idea and a waste of YOUR money!

Nikon Z7

And NO – this title isn’t meant as clickbait!

I love Nikon cameras for many reasons.

I HATE Nikon as a company.

I dislike Canon cameras for numerous technical and ergonomic reasons.

I LIKE Canon as a company.

The Nikon D5 was THE FIRST Nikon camera I’ve used that I dislike and thought was like the proverbial bag of spanners.

But now there’s a new Nikon that takes over the mantle of Nikon at its very worst – and I’ve not even clapped eyes on one yet let alone handled one.  I don’t need to play with one to know just how much of a rip-off this pile of rubbish really is.

This camera is £4000 at Wex here in the UK – yes, that FOUR THOUSAND of your hard-earned spondoolicks (for our overseas friends that’s ‘slang’ for pounds sterling).

We’ve already harangued the Z7 for its single media slot – and Canon followed suit with the EOS R, is that a coincidence?

But here’s the kicker, and the MAIN reason why the Nikon Z7 is a crock, and the indicator lies at the foot of page 57 in the Nikon Z7 user manual:

Nikon Z7

And for those with bad eyesight:

Nikon Z7

You can see/download the manual here: NIKON Z7 USER MANUAL

I think the first to show the AF problems with the Nikon Z7 was the ‘afro haircut idiot know-nothing from Philedelphia’ – you know, the guy who never knew how to use Photoshop until the other month when Matt Kloskowski showed him how – live on YouTube.

Lot’s of people are jumping on the DISS THE NIKON Z7 AF bandwagon as I’m typing this, but none of the morons are pointing out WHY the NIKON Z7 auto focus is so crappy.

So I will tell you why!!!!

There is no way to have any control finesse over the AF functionality.

Nikon Z7

Above is the main control functionality for the D5/500/850 MultiCAM 20K AF system.

You will see controls for Blocked Shot Response and Subject Motion.  These roughly equate to Tracking Sensitivity and Acceleration/Deceleration Tracking on the controls for the Canon 61 point Reticular system found on the likes of the 1DX Mk1 and Mk2 and 5DMk 3 and Mk4.

The two controls on both Nikon and Canon dictate the auto focus SOLUTION spat out by the PREDICTIVE AF ALGORITHMS contained in the cameras AF engine processors.

The subjects degree and type of motion RELATIVE to the camera position DEMAND different setups within this control panel.  It’s all to do with the camera AF resistance to MINOR and MAJOR changes in subject position between one frame and the next.

If you want a definitive understanding of all this then go and purchase my Autofocus Guide to Nikon and Canon AF for Long Lenses and Birds in Flight by clicking this link.

So this is the problem with the Nikon Z7 – because it’s utilizing so-called ‘on chip phase detect’ – which isn’t phase detect at all in reality – you cannot get control of these variable functions because they don’t exist in the cameras menu/firmware.

As far as I’m aware these sorts of controls are not available on the Sony cameras either.

But there is still a form of predictive AF algorithm at work in all mirrorless cameras, and it would appear that the one inside the Nikon Z7 is really poor in the way it’s balanced out with regard to it coping with moving subjects – especially those that move somewhat erratically and towards the camera.

Understand this people, the Nikon Z7 is a glorified D5000 that is not worth half the price you’ll have to pay for it.

Mirrorless systems have certain advantages over traditional dSLR systems:

  • Reduction in Shutter Lag times
  • Removal of Mirror Slap vibrations
  • Reduction of Weight leading to Greater Portability

But on-chip phase detection isn’t real phase detection, and it will not (for the foreseeable future) be anywhere near as fast or accurate as CORRECTLY setup phase detect autofocus on a top flight dSLR.

A sequence of 77 raw files that are all tack sharp and cover around 12 seconds of time – no mirrorless system is capable of doing this to the same degree of consistency as a correctly set dSLR.

The dSLR is NOT DEAD!

Don’t believe me?

Licensed Formula 1 pit and circuit access photographers make a very good living, and they stand or fall by the reliability of their camera gear.  But they are all business people at the end of the day.

If a Sony A9 and that fancy 400mm Sony lens was as reliable as the Sony fanboys claim it is, then why will we not see a plethora of Sony rigs at Suzuka on Sunday?  Just a thought…

But for heavens sake folks, if you have a hankering for a Nikon Z7 then PLEASE think about it – make yourself aware of the FACTS before you blow your wodge of wonga!

It’s NOT a professional camera in any way shape or form, and Dirk Jasper of Nikon Europe even says that – watch the video below at 19mins 48sec:

NOTE TO NIKON:  If you want to try and get me to change my mind then all you have to do is send me one guys!

I promise I won’t lick it or sniff it like that Jared Polin idiot!

 

 

Nikon D5

Posted on by
Reply

Nikon D5 – My Initial Thoughts

Nikon D5

Nikon D5

My initial thoughts/questions about this much-awaited offering from Nikon have always revolved around ONE item – AUTOFOCUS.

For a long time Canon have had the march on Nikon in the AF department – simply because of the “customisation” of the cameras AF operating criteria Canon give their users.

Nowhere is this more apparent than in the speed machine Canon 1DX in comparison with Nikons D4/D4S.

Nikon have only ever allowed a customisable Focus Tracking with lock-on (FTLo):

_D3C6345

Whereas Canon give us:

_DSC3994

Nikon FTLo equates directly with Canon Tracking Sensitivity (TS), but Canon gives you custom control over Acceleration/Deceleration Tracking (ADT) – something that Nikon have consistently failed to do.

On the D4S etc there are two ADT presets, but you can’t access them directly because they are hidden inside the Dynamic Area AF modes.

I’m not going to explain in detail what ADT and TS/FTLo do – for that you’ll need to obtain my AF Guide HERE – but in very simple terms Canon TS/Nikon FTLo control the autofocus system resistance to MAJOR CHANGE and Canon ADT controls its resistance to MINOR CHANGE – two massively different variants that can effect huge differences in autofocus performance on moving subjects.

And it’s this lack of control over resistance to MINOR change independent of MAJOR change resistance settings on Nikon that is responsible for the superiority of the Canon system.

So, Nikon had the opportunity to draw level with Canon on this front with the new D5.

Have they done so?

Well, they won’t lend me one to test, and I can’t afford to order one, but after doing some digging around I find the answer (in principle anyway):

Nikon D5 and D500 Autofocus customisable settings.

Nikon D5 and D500 Autofocus customisable settings.

YES – they have (as long as it works in practise that is!).

The FTLo menu now has two variables – Blocked Shot Response; which is the conventional Nikon custom control though under a name/title that’s more indicative of its function.

But now Nikon offer us Subject Motion too – and it’s this control function that I’ve been crying out for.  This equates to Canon ADT or Acceleration/Deceleration tracking.

My experiences with Canon have always led me to discount -2 and +2 ADT settings, as in my own Bird in Flight photography terms they bring nothing to the table.  So perhaps Nikon have really done their homework for once.

The other improvement I like is the 2x XQD slot option for the Nikon D5 – that would make my life a heck of a lot easier for sure.

Nothing else really excites me about the new Nikon D5 – and the touch screen on the back might prove to be less than a fun thing when wearing gloves in -20C conditions.

But the potential for the new Multicam 20K AF system is what excites me the most; it theoretically puts this DSLr body at the top of the pile for wildlife photography.

It’s not often I see a new body that I wish I could get my hands on immediately but the D5 is different – I want one NOW!

ADDENDUM

It would appear that there is a short-coming on the D5 4K video recording facility – see here.

For recording stock clips this wouldn’t be a problem for me, but a maximum of 3 minutes of 4K recording might not suite everyone.  Is there a sensor over-heat problem?

Strangely the D500 can do 30 minutes with a cropped sensor – which should run hotter you’d think.

If there are things “wrong” with the D5 now, and they are not corrected by the time they hit the retailers, or by the first firmware update BE CAREFUL…

This is where D4 buyers got caught out – they wait 12 months and bring out an S-version.

Become a patron from as little as $1 per month, and help me produce more free content.

Patrons gain access to a variety of FREE rewards, discounts and bonuses.

Autofocus Guide for Long Lens Bird in Flight Photography

Posted on by
1

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 which he has just caught.

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.

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.

Become a patron from as little as $1 per month, and help me produce more free content.

Patrons gain access to a variety of FREE rewards, discounts and bonuses.

Image Sharpness

Posted on by
2

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 sharpness, Andy Astbury, Wildlife in Pixels, Red Kite

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 sharpness, Andy Astbury, Wildlife in Pixels, Red Kite

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

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

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

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 sharpness, Andy Astbury, Wildlife in Pixels, Red Kite

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:

  1. Changing spatial relationship between camera and subject during a burst of frames.
  2. Subject-to-camera closing speed
  3. Pre-shot tracking time.
  4. 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 sharpness, Andy Astbury, Wildlife in Pixels, Red Kite

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

Understanding Canon & Nikon Autofocus for Bird in Flight Photography

Click Image for details.

Become a patron from as little as $1 per month, and help me produce more free content.

Patrons gain access to a variety of FREE rewards, discounts and bonuses.

View Autofocus Points in Lightroom

Posted on by
Reply

Mr. Malcolm Clayton sent me a link last week to a free plug-in for Lightroom that displays the autofocus points used for the shot, plus other very useful information such as focus distance, f-number and shutter speed, depth of field (DoF) values and other bits and bobs.

The plug-in is called “Show Focus Points” and you can download it HERE

Follow the installation instruction to the letter!

Once installed you can only launch it from the LIBRARY MODULE:

Accessing the Plug-in via the Library>Plug-in Extras menu

Accessing the Plug-in via the Library>Plug-in Extras menu CLICK to view LARGER

You will see this sort of thing:

The "Show Focus Points" for Lightroom plug-in window.

The “Show Focus Points” for Lightroom plug-in window. CLICK to view LARGER.

It’s a usefull tool to have because short of running the rather clunky Canon DPP or Nikon ViewNX software it’s the easiest way of getting hold of autofocus information without sending the image to Photoshop and looking through the mind-numbing RAW schema data – something I do out of habbit!

It displays a ton of useful data about your camera focus settings and exposure, and the autofocus point used – be it set by you, or chosen by the camera.

As far as I can see, the plug-in only displays the main active autofocus point on Nikon D4 and D4S files, but all the autofocus group as well as active points seem to display when viewing .CR2 Canon files as we can see on this very impressive car number plate!:

Screen grab of an unprocessed 1Dx/200-400/TC shot I did while testing the tracking capabilities of the Canon lens with the TC active - the REAL image looks more impressive than this!

Screen grab of an unprocessed 1Dx/200-400/TC shot I did while testing the tracking capabilities of the Canon lens with the TC active – the REAL image looks more impressive than this! I’m actually zooming out while tracking too – this is around 200mm + the 1.4x TC. CLICK to view LARGER

Canon 1Dx in AF Point Expansion 4 point; what I call "1 with 4 friends".

Canon 1Dx in AI Servo AF Point Expansion 4 point; what I call “1 with 4 friends”. CLICK to view LARGER.

Canon 1Dx in AI-F autofocus showing all autofocus points used be the camera.

Canon 1Dx in AI-F autofocus showing all autofocus points used be the camera.

Viewing your autofocus points is a very valid learning tool when trying to become familiar with your cameras autofocus, and it’s also handy if you want to see why and where you’ve “screwed the pooch” – hey, we ALL DO IT from time to time!

Useful tool to have IMO and it’s FREE – Andy likes free…

Cheers to Malc Clayton for bringing this to my attention.

Become a patron from as little as $1 per month, and help me produce more free content.

Patrons gain access to a variety of FREE rewards, discounts and bonuses.

Autofocus Drill-down

Posted on by
4

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.

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.

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:

  1.  lens resolving power – small, fine details need to be as close as possible.*
  2.  sensor resolving power – we need as many pixels as possible covering the subject.*
  3.  auto focus point placement accuracy – if the subject is too small in the frame, point placement is inaccurate.
  4. 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.

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!

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.

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:

  1. the depth of field at those distances is large.
  2. 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:

  1. he/she has got little or no depth of field
  2. 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.

Become a patron from as little as $1 per month, and help me produce more free content.

Patrons gain access to a variety of FREE rewards, discounts and bonuses.

Auto Focus & Shooting Speed

Posted on by
3

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:

 

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

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:

  1. Mirror lifts
  2. Front shutter curtain falls
  3. Rear shutter curtain falls
  4. 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!

Become a patron from as little as $1 per month, and help me produce more free content.

Patrons gain access to a variety of FREE rewards, discounts and bonuses.