Image Retouching

Posted on May 11, 2015 by Andrew Astbury

Image Retouching in Photoshop CC 2014

It’s very rare that we ever get a frame from our camera that doesn’t need retouching – that’s a FACT.

Imperfections in the frame can be both ‘behind the shutter’ and ‘in front of the lens’ – sensor dust and crud on the subject. But you’ll take photographs where these imperfections are hard, if not impossible, to see under normal viewing.

But print that image BIG and those invisible faults will begin to be visually apparent; by which time it’s too bloomin’ late and they’ve cost you money; or worse still, a client.

The ‘visualise spots’ tool in Lightroom will show you a certain amount of ‘dust bunny’ type faults and errors, but the way Lightroom executes retouching repairs is not always ‘quite up to snuff’; and when it comes to dust, crap and other undesirables on the subject itself Lightroom will fail to recognise them in the first place.

Image retouching isn’t really all that difficult; but it can be an intensely tedious and time-consuming process.

To that end I’ve stuck these HD video lessons on my You Tube channel.

In these videos I illustrate how I deploy the Spot Healing brush, Healing Brush, Clone Tool, Patch Tool and Content Aware Fill command to carry out some basic image retouching on a shot of cutlery bright ware.

I demonstrate the addition of a ‘dust visibility’ curves adjustment layer – something that everyone should ‘get the hang’ of using – as a first step to effective image retouching.

When photographing glossy, high reflectivity subjects we need to remove the imperfections and smooth the surfaces of the subject without reducing the ‘glossiness’ and turning it matt!

Please note: a couple of these videos are in excess of 20 minutes duration and they will look better at full resolution HDV if you click the You Tube icon. Also, it takes a lot longer to do a job when you have to talk about at the same time!

I hope you get some idea as to how simple and straightforward my approach to image retouching is!

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Lumenzia for Wildlife

Posted on March 14, 2015 by Andrew Astbury

The Lumenzia Photoshop extension

Yet more on the usefulness of the Lumenzia Photoshop extension, the short cut to great looking images of all types and styles.

I had an email from client and blog follower David Sparks after my last post about this useful mighty Photoshop tool.

He sent these before and after rail shots:

Before adding Lumenzia. Click for larger view.

After adding Lumenzia. Click for larger view.

Comparison overlay – see how the left side of the image has that extra presence – and that’s just with the click of a couple of buttons in the Lumenzia GUI. Click to view larger.

Here is what David had to say in his email:

Andy, here is a before and after. Processing was much, much faster than usual, using Lumenzia.

Thanks for bringing it to my attention….I’m working my way through your Image Processing in LR4 & Photoshop + LR5 bundle and enjoying it very much.

And as my friend and blog follower Frank Etchells put it:

Excellent recommendation this Andy. Bought it first time from your previous posting… at just over £27 it’s marvellous

What gets me puzzled is the fact that these Lumenzia posts have had over 500 separate page views in the last few days but less then 3% of you have bought it – WTF are you guys waiting for…

Get it BOUGHT – NOW – HERE

UPDATE: Greg Benz (the plugin author) has launched a comprehensive Lumenzia training course – see my post here for more information.

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Colour Editing in Photoshop

Posted on March 13, 2015 by Andrew Astbury

Colour Editing in Photoshop using the Channel Mixer

I’ve just uploaded 3 video lessons on THE BEST way to do selective colour changes in Photoshop using the Channel Mixer.

This is a far better and more accurate way to change the colour of something whilst maintaining all its original tonality, and it is vastly better than the commonly touted Hue saturation method.

HueSat doesn’t do the job with 100% fidelity, and you are very limited in the colour choice.

Using the Channel Mixer method you can effectively make every single colour in the Pantone colour spectrum simply by using Pantone/RGB conversion figures.

If you watch the videos on YouTube it may take a minute for the HD play option to activate.

Part 1 is here:

Part 2 here:

Part 3 here:

The demo file can be downloaded on the link below:

https://dl.dropboxusercontent.com/u/87066369/Caterham.psd.zip

There are many instances where you might want or need to change the colour of an object in your image, and this is exactly what the Channel Mixer exists for; not for creating crappy black and white conversions as some crackpots think.

Give it a try for yourself by downloading the file and following along with the videos – the file has the path built into it, put these paths are simple to make with then pen tool.

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Lumenzia – Not Just for Landscapes

Posted on March 11, 2015 by Andrew Astbury

Luminosity Masking is NOT just for landscape photographs – far from it.

But most folk miss the point of luminosity masking because they think it’s difficult and tedious.

The point, as I always see it, is that luminosity masking allows you to make dramatic but subtle changes and enhancements to your image with what are actually VERY fast and crude “adjustments”.

This in reality means that luminosity masking is FAST – and way faster than trying to do “localised” adjustments. But the creation of the masks and choosing which one to use is what crippled the “ease factor” for most.

But with this new Lumenzia extension is so snappy and quick at showing you the different masks that, if you know what area of the image you want to adjust, the whole process takes SECONDS.

Let’s look at a White-tailed Eagle taken just 15 days ago:

Straight off the 1Dx it looks like this:

RAW unprocessed .CR2 file (CLICK to view in new window)

Inside the Develop Module of Lightroom 5 it looks like:

RAW unprocessed – (CLICK to view in new window)

A few tweaks later and it looks like:

Tweaks are what you can see in the Basics Panel + CamCal set to Neutral, and Chroma Noise removal in the Lens Corrections Panel is turned ON – (CLICK to view in new window)

Sending THIS adjusted image to Photoshop:

(CLICK to view in new window)

All I want to do is give a “lift” to the darker tones in the bird; under the wings, and around the side of head, legs and tail.

Using a BRUSH to do the job is all fine ‘n dandy BUT, you would be creating a localised adjustment that’s all-encompassing from a tonal perspective; all tones that fell under the brush get adjusted by the same amount.

A luminosity mask, or indeed ANY pixel-based mask is exactly what it says it is – a mask full of pixels. And those pixels are DERIVED from the real pixels in your image. But the real beauty is that those pixels will be anywhere from 1% to 100% selected, or not selected at all.

Where they are 100% selected they are BLACK, and any adjustment you make BEHIND that mask will NOT be visible.

Pixels that are NOT selected will be WHITE, and your adjustment will show fully.

But where the pixels are between 1% and 99% selected they will appear as 1% GREY to 99% grey and so will show or hide variation of said adjustment by the same amounts…got it?

The Lumenzia D4 mask looks like it’ll do the job I want:

Lumenzia D4 mask (CLICK to view in new window)

Click the image to view larger – look at the subtle selections under those wings – try making that selection any other way in under 2 seconds – you’ve got no chance!

The “lift” I want to make in those WHITER areas of the mask is best done with a Curves Adjustment layer:

Select “Curve” in the Lumenzia GUI – (CLICK to view in new window)

So hit the Curve button and voilà:

The Lumenzia D4 mask is now applied to Curves Adjustment Layer – (CLICK to view in new window)

You can see in the image above that I’ve made a very rough upwards deflection of the curve to obtain an effective but subtle improvement to those under-wing areas etc. that I was looking to adjust.

The total time frame from opening the image in Photoshop to now is about 20 seconds! Less time than the Lightroom 5 adjustments took…

And to illustrate the power of that Lumenzia D4 Luminosity mask, and the crudity of the adjustment I made, here’s the image WITHOUT THE MASK:

The effect of the luminosity mask is best illustrated by “hiding” it – bloody hell, turn it back on ! – (CLICK to view in new window).

And at full resolution you can see the subtleties of the adjustment on the side of the head:

With Lumenzia (left) and just the Lightroom 5 processing (right) – (CLICK to view in new window).

If you want to get the best from your images AND you don’t want to spend hours trying to do so, then Lumenzia will seriously help you.

Clicking this link HERE to buy Lumenzia doesn’t mean it costs you any more than if you buy it direct from the developer. But it does mean that I get a small remuneration from the developer as a commission which in turn supports my blog. Buying Lumenzia is a total no-brainer so please help support this blog by buying it via these links – many thanks folks.

UPDATE June 2018: Greg Benz (the plugin author) has launched a comprehensive Lumenzia training course – see my post here for more information.

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Lumenzia for Easy Luminosity Masking

Posted on March 9, 2015 by Andrew Astbury

Lumenzia for Easy Luminosity Masking..

I’m a really BIG user of luminosity masking techniques, and the ease by which you can use them to create really powerful adjustments to your image inside Photoshop – adjustments that are IMPOSSIBLE to make in Lightroom.

For a while now I’ve been selling a luminosity mask action set for Photoshop, and up until a week ago I had plans to upgrade said action set to produce even more custom masks.

That is until a good friend of mine, Mr. Omar Jabr, asked me if I’d come across this new product, LUMENZIA, that made the production and deployment of luminosity masks and their derivatives EVEN EASIER.

Lumenzia,luminosity masking,Andy Astbury,Wildlife in Pixels Blog

An original RAW file open in Lightroom (right) together with the final image (left) – 99% of the “heavy lifting” being done in Photoshop using the Lumenzia Extension and it’s luminosity masking functions.

In all honesty I am so excited about this amazing software extension that I’ve abandoned all plans to further develop my own action set for Photoshop – to do so would be a truly pointless exercise.

There is so much more to Lumenzia than the production of the standard 4 or 5 Darks,Lights and Midtone luminosity masks that mine and other available action sets produce.

To get an idea of just how powerful Lumenzia is just click HERE to visit the applications home page – and just buy it while you are there; purchase is a “no brainer” and one of those digital imaging JDI’s (just do it)!

The inclusion of a luminosity masking function based on the Zone System gives you instant recourse to masks based on Ansel Adams 11 zone system of scene brightness – a classic approach to the quantification of subject brightness range created by arguably the greatest landscape photographer the world has ever known – IMHO of course.

In order to instal Lumenzia you will need to install the correct Photoshop Extension Manager for which ever version of Photoshop you are running – CS6, CC, or CC2014 (it is not intended to be installed on CS5 or lower).

1. Buy Lumenzia

2. Follow the download link, and download the .Zip folder.

3. Extract the folder contents.

4. Locate the “com.lumenzia.zxp” file in the extracted contents, right click and choose Open with: Adobe Extension Manager v.xx

You should see:

Click Install, and you should see:

If you are running Mac OS 10.10x Yosemite you may have a slight problem with the CC2014 Extension Manager not being able to find the application pathway to Ps CC2014. If you get a message from the Extension Manager waffling on about needing Photoshop v11 or higher don’t stress, the fix is a little brutal but really simple:

Go Applications>Utilities>Adobe Installers and UNINSTALL (that’s right!) BOTH Photoshop CC2014 and Extension Manager CC2014, then log back in to your CC account, go to the Apps tab and re-install Photoshop CC2014 AND Extension Manager CC2014 sequentially – that will cure the problem and only take about 5 or 6 minutes.

Open a RAW file in CameraRAW, or better still Lightroom. Get your camera calibration and contrast under control as I’ve banged on about so many times before, negate any chromatic aberration and do a bit of effective noise reduction if needed, then send the image to Photoshop:

Go Window>Extensions>Lumenzia

Go Window>Extensions>Lumenzia and the Lumenzia interface will appear – I like to drag it into the right hand tools palette so it’s not encroaching on the work area.

The first thing that amazed me about Lumenzia is the fact that you can create luminosity masks without creating 12 or 15 separate Alpha channels with the image – this makes a HUGE difference to the file size of the image, not just from the disc space PoV but it can also have file handling speed benefits in terms of tile rendering speed and scratch disc usage – if you don’t understand that just think of it as a GOOD thing!

For example:

The final adjusted image (prior to a couple of tweaks in Lightroom) on the left is 271Mb including all layers being intact; the image on the right, though not yet processed, has been prepared for processing by running a luminosity mask action set and developing a stack of Alpha channels; it is now over 458Mb:

…just because of the Alpha channels. And we have also got 50 steps of History that have to be retained by Photoshop; as you’ve now realised, the joke is that it’s double the size of the Lumenzia processed image and we haven’t begun to start making any adjustments yet!

There is lot’s more to Lumenzia, such as surface sharpening and easy dodge and burn layer creation – it’s going to take me a week to digest it all.

Prior to working with Lumenzia my one question was “how good are the masks” – well they are pixel-perfect.

Creating pixel-perfect luminosity masks is the most tedious of jobs if you do it the maual way – so much so that most folk take one look at the process and go “No thanks…..”

Photographers like myself couldn’t really help alleviate the tedium until the advent of CS6 which gave us the ability to write an ACTION that involved the operation of a PREVIOUSLY recorded action – so the luminosity mask action set was born.

But the developer of Lumenzia has topped it all by the proverbial country mile and given us a totally unique way of making the tedious and complex very easy and simple.

Once you have made your purchase you’d do well to go and watch the developer videos that are available online; you will get links to the training and support pages in your purchase receipt.

And to top it all off we can even generate Alpha channels and selections if we want or need to, and we can mask on the basis of Vibrancy and Saturation; yet another processing wheeze known by few, and used by fewer still.

The developer has given me permission to demonstrate and teach the deployment of Lumenzia, and to promote it as an affiliate. I’ve been offered affiliate-ships before but have rejected them in the past because basically what was being peddled was either crap or too expensive; or BOTH.

But whatever you think the opinion of yours truly is worth, I can honestly say that Lumenzia is most definitely NEITHER of the above – it’s that good I’ll never use anything else ever again, and at under 40 bucks you’re going to make one hell of a difference to your images with so little effort it’s unreal.

Click HERE to buy and download

LUMENZIA – BUY IT – go on, get on with it!

Lumenzia GUI for Photoshop CC2014

UPDATE June 2018: Greg Benz (the plugin author) has launched a comprehensive Lumenzia training course – see my post here for more information.

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Camera Calibration

Posted on September 29, 2014 by Andrew Astbury

Custom Camera Calibration

The other day I had an email fall into my inbox from leading UK online retailer…whose name escapes me but is very short… that made my blood pressure spike. It was basically offering me 20% off the cost of something that will revolutionise my photography – ColorChecker Passport Camera Calibration Profiling software.

I got annoyed for two reasons:

Who the “f***” do they think they’re talking to sending ME this – I’ve forgotten more about this colour management malarkey than they’ll ever know….do some customer research you idle bastards and save yourselves a mauling!
Much more importantly – tens of thousands of you guys ‘n gals will get the same email and some will believe the crap and buy it – and you will get yourselves into the biggest world of hurt imaginable!

Don’t misunderstand me, a ColorChecker Passport makes for a very sound purchase indeed and I would not like life very much if I didn’t own one. What made me seethe is the way it’s being marketed, and to whom.

Profile all your cameras for accurate colour reproduction…..blah,blah,blah……..

If you do NOT fully understand the implications of custom camera calibration you’ll be in so much trouble when it comes to processing you’ll feel like giving up the art of photography.

The problems lie in a few areas:

First, a camera profile is a SENSOR/ASIC OUTPUT profile – think about that a minute.

Two things influence sensor/asic output – ISO and lens colour shift – yep. that’s right, no lens is colour-neutral, and all lenses produce colour shifts either by tint or spectral absorption. And higher ISO settings usually produce a cooler, bluer image.

Let’s take a look at ISO and its influence on custom camera calibration profiling – I’m using a far better bit of software for doing the job – “IN MY OPINION” – the Adobe DNG Profile Editor – free to all MAC download and Windows download – but you do need the ColorChecker Passport itself!

I prefer the Adobe product because I find the ColorChecker software produced camera calibration profiles there were, well, pretty vile in terms of increased contrast especially; not my cup of tea at all.

5 images shot at 1 stop increments of ISO on the same camera/lens combination.

Now this is NOT a demo of software – a video tutorial of camera profiling will be on my next photography training video coming sometime soon-ish, doubtless with a somewhat verbose narrative explaining why you should or should not do it!

Above, we have 5 images shot on a D4 with a 24-70 f2.8 at 70mm under a consistent overcast daylight at 1stop increments of ISO between 200 and 3200.

Below, we can see the resultant profile and distribution of known colour reference points on the colour wheel.

Here’s the 200 ISO custom camera calibration profile – the portion of interest to us is the colour wheel on the left and the points of known colour distribution (the black squares and circled dot).

Next, we see the result of the image shot at 3200 ISO:

Here’s the result of the custom camera profile based on the shot taken at 3200 ISO.

Now let’s super-impose one over t’other – if ISO doesn’t matter to a camera calibration profile then we should see NO DIFFERENCE………….

The 3200 ISO profile colour distribution overlaid onto the 200 ISO profile colour distribution – it’s different and they do not match up.

……..well would you bloody believe it! Embark on custom camera calibration profiling your camera and then apply that profile to an image shot with the same lens under the same lighting conditions but at a different ISO, and your colours will not be right.

So now my assertions about ISO have been vindicated, let’s take a look at skinning the cat another way, by keeping ISO the same but switching lenses.

Below is the result of a 500mm f4 at 1000 ISO:

Profile result of a 500mm f4 at 1000 ISO

And below we have the 24-70mm f2.8 @ 70mm and 1000 ISO:

Profile result of a 24-70mm f2.8 @ 70mm at 1000 ISO

Let’s overlay those two and see if there’s any difference:

Profile results of a 500mm f4 at 1000 ISO and the 24-70 f2.8 at 1000 ISO – as massively different as day and night.

Whoops….it’s all turned to crap!

Just take a moment to look at the info here. There is movement in the orange/red/red magentas, but even bigger movements in the yellows/greens and the blues and blue/magentas.

Because these comparisons are done simply in Photoshop layers with the top layer at 50% opacity you can even see there’s an overall difference in the Hue and Saturation slider values for the two profiles – the 500mm profile is 2 and -10 respectively and the 24-70mm is actually 1 and -9.

The basic upshot of this information is that the two lenses apply a different colour cast to your image AND that cast is not always uniformly applied to all areas of the colour spectrum.

And if you really want to “screw the pooch” then here’s the above comparison side by side with with the 500f4 1000iso against the 24-70mm f2.8 200iso view:

500mm f4/24-70mm f2.8 1000 ISO comparison versus 500mm f4 1000 ISO and 24-70mm f2.8 200 ISO.

A totally different spectral distribution of colour reference points again.

And I’m not even going to bother showing you that the same camera/lens/ISO combo will give different results under different lighting conditions – you should by now be able to envisage that little nugget yourselves.

So, Custom Camera Calibration – if you do it right then you’ll be profiling every body/lens combo you have, at every conceivable ISO value and lighting condition – it’s one of those things that if you don’t do it all then you’d be best off not doing at all in most cases.

I can think of a few instances where I would do it as a matter of course, such as scientific work, photo-microscopy, and artwork photography/copystand work etc, but these would be well outside the remit the more normal photographic practices.

As I said earlier, the Passport device itself is worth far more than it’s weight in gold – set up and light your shot and include the Passport device in a prominent place. Take a second shot without it and use shot 1 to custom white balance shot 2 – a dead easy process that makes the device invaluable for portrait and studio work etc.

But I hope by now you can begin to see the futility of trying to use a custom camera calibration profile on a “one size fits all” basis – it just won’t work correctly; and yet for the most part this is how it’s marketed – especially by third party retailers.

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Parallel Horizontals.

Posted on May 25, 2014 by Andrew Astbury

Quite often when shooting landscapes, or more commonly seascapes, you may run into a problem with parallel horizontals and distortion between far and near horizontal features such as in the image below.

Parallel horizontals that are not parallel – but should be!

This sort of error cannot be fully corrected in Lightroom alone; we have to send the image to Photoshop in order to make the corrections in the most efficient manner.

Here’s a video lesson on how to effectively do just that, using the simplest, easiest and quickest of methods:

You can watch the video at full size HERE – make sure you click the HD icon.

This is something which commonly happens when photographing water with a regular shaped man-made structure in the foreground and a foreshortened horizon line such as the receding opposite shore in this shot. But with a little logical thought these problems with parallel horizontals being “out of kilter” can be easily cured.

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Paper White – Desktop Printing 101

Posted on February 17, 2014 by Andrew Astbury

Paper White video

A while back I posted an article called How White is Paper White

As a follow-up to my last post on the basic properties of printing paper media I thought I’d post this video to refresh the idea of “white”.

In this video we basically look at a range of 10 Permajet papers and simply compare their tints and brightness – it’s an illustration I give at my print workshops which never fails to amaze all the attendees.

I know I keep ‘banging on’ about this but you must understand:

Very few paper whites are even close to being neutral.
No paper is WHITE in terms of luminosity – RGB 255 in 8 bit colour terms.
No paper can hold a true black – RGB 0 in 8 bit colour terms.

In real-world terms ALL printing paper is a TINTED GREY – some cool, some warm.

If we attempted to print the image above on a cool tinted paper then we would REDUCE or even CANCEL OUT the warm tonal effects and general ‘atmosphere’ of the image.

Conversely, print it to a warmer tinted ‘paper white’ and the atmosphere would be enhanced.

Would this enhancement be a good thing? Well, er NO – not if we were happy with our original ‘on screen’ processing.

You need to look upon ‘paper white’ as another TOOL to help you achieve your goal of great looking photographs, with a minimum of fuss and effort on your part.

We have to ‘soft proof’ our images if we want to get a print off the printer that matches what we see on our monitor.

But we can’t soft proof until we have made a decision about what paper we are going to soft-proof to.

Choosing a paper who’s characteristics match our finished ‘on screen’ image in terms of TINT especially, will make the job of soft proofing much easier.

How, why?

Proper soft proofing requires us to make a copy of our original image (there’s most peoples first mistake – not making a copy) and then making adjustments to said copy, in a soft proof environment, so that it it renders correctly on the print – in other words it matches our original processed image.

Printing from Photoshop requires a hard copy, printing from Lightroom is different – it relies on VIRTUAL copies.

Either way, this copy and its proof adjustments are what get sent to the printer along what we call the PRINT PIPELINE.

The print pipeline has to do a lot of work:

It has to transpose our adjusted/soft proofed image colour values from additive RGB to print CMYK
It has to up sample or interpolate the image dpi instructions to the print head, depending on print output size.
It has to apply the correct droplet size instructions to each nozzle in the print head hundreds of times per second.
And it has to do a lot of other ‘stuff’ besides!!

The key component is the Printer Driver – and printer drivers are basically CRAP at carrying out all but the simplest of instructions.

In other words they don’t like hard work.

Printing to a paper white that matches our image:

Warm image to warm tint paper white

Cool image to cool paper white

will reduce to the amount of adjustments we have to make under soft proofing and therefore REDUCE the printer driver workload.

The less work the print driver has to do, the lower is the risk of things ‘getting lost in translation‘ and if nothing gets lost then the print matches the on screen image – assuming of course that your eyes haven’t let you down at the soft proofing stage!

IMPORTANT – Click Image to Enlarge in new window

If we try to print this squirrel on the left to Permajet Gloss 271 (warmish image to very cool tint paper white) we can see what will happen.

We have got to make a couple of tweaks in terms on luminosity BUT we’ve also got to make a global change to the overall colour temperature of the image – this will most likely present us with a need for further opposing colour channel adjustments between light and dark tones.

IMPORTANT – Click Image to Enlarge in new window

Whereas the same image sent to Permajet Fibre Base Gloss Warmtone all we’ll have to do is tweak the luminosity up a tiny bit and saturation down a couple of points and basically we’ll be sorted.

So less work, and less work means less room for error in our hardware drivers; this leads to more efficient printing and reduced print production costs.

And reduced cost leads to a happy photographer!

Printing images is EASY – as long as you get all your ducks in a row – and you’ve only got a handful of ducks to control.

Understanding print media and grasping the implications of paper white is one of those ducks………

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Gamma Encoding – Under the Hood

Posted on January 29, 2014 by Andrew Astbury

Gamma, Gamma Encoding & Decoding

Gamma – now there’s a term I see cause so much confusion and misunderstanding.

So many people use the term without knowing what it means.

Others get gamma mixed up with contrast, which is the worst mistake anyone could ever make!

Contrast controls the spatial relationship between black and white; in other words the number of grey tones. Higher contrast spreads black into the darker mid tones and white into the upper mid tones. In other words, both the black point and white point are moved.

The only tones that are not effected by changes in image gamma are the black point and white point – that’s why getting gamma mixed up with contrast is the mark of a “complete idiot” who should be taken outside and summarily shot before they have chance to propagate this shocking level of misunderstanding!

What is Gamma?

Any device that records an image does so with a gamma value.

Any device which displays/reproduces said image does so with a gamma value.

We can think of gamma as the proportional distribution of tones recorded by, or displayed on, a particular device.

Because different devices have different gamma values problems would arise were we to display an image that has a gamma of X on a display with a gamma of Y:

Ever wondered what a RAW file would look like displayed on a monitor without any fancy colour & gamma managed software such as LR or ACR?

A raw file displayed on the back of the camera (left) and as it would look on a computer monitor calibrated to a gamma of 2.2 & without any colour & gamma management (right).

The right hand image looks so dark because it has a native gamma of 1.0 but is being displayed on a monitor with a native gamma of 2.2

RAW file Gamma

To all intents and purposes ALL RAW files have a gamma of 1.0

Camera Sensor/Linear Gamma (Gamma 1.0)

Digital camera sensors work in a linear fashion:

If we have “X” number of photons striking a sensor photosite then “Y” amount of electrons will be generated.

Double the number of photons by doubling the amount of light, then 2x “Y” electrons will be generated.

Halve the number of photons by reducing the light on the scene by 50% then 0.5x “Y” electrons will be generated.

We have two axes on the graph; the horizontal x axis represents the actual light values in the scene, and the vertical y axis represents the output or recorded tones in the image.

So, if we apply Lab L* values to our graph axes above, then 0 equates to black and 1.0 equates to white.

The “slope” of the graph is a straight line giving us an equal relationship between values for input and output.

It’s this relationship between input and output values in digital imaging that helps define GAMMA.

In our particular case here, we have a linear relationship between input and output values and so we have LINEAR GAMMA, otherwise known as gamma 1.0.

Now let’s look at a black to white graduation in gamma 1.0 in comparison to one in what’s called an encoding gamma:

Linear (top) vs Encoded Gamma

The upper gradient is basically the way our digital cameras see and record a scene.

There is an awful lot of information about highlights and yet the darker tones and ‘shadow’ areas are seemingly squashed up together on the left side of the gradient.

Human vision does not see things in the same way that a camera sensor does; we do not see linearly.

If the amount of ambient light falling on a scene suddenly doubles we will perceive the increase as an unquantifiable “it’s got brighter”; whereas our sensors response will be exactly double and very quantifiable.

Our eyes see a far more ‘perceptually even’ tonal distribution with much greater tonal separation in the darker tones and a more compressed distribution of highlights.

In other words we see a tonal distribution more like that contained in the gamma encoded gradient.

Gamma encoding can be best illustrated with another graph:

Linear Gamma vs Gamma Encoding 1/2.2 (0.4545)

Now sadly this is where things often get misunderstood, and why you need to be careful about where you get information from.

The cyan curve is NOT gamma 2.2 – we’ll get to that shortly.

Think of the graph above as the curves panel in Lightroom, ACR or Photoshop – after all, that’s exactly what it is.

Think of our dark, low contrast linear gamma image as displayed on a monitor – what would we need to do to the linear slope to improve contrast and generally brighten the image?

We’d bend the linear slope to something like the cyan curve.

The cyan curve is the encoding gamma 1/2.2.

There’s a direct numerical relationship between the two gamma curves; linear and 1/2.2. and it’s a simple power law:

V_O = V_I^γwhere V_O = output value, V_I = input value and γ = gamma

Any input value (V_I) on the linear gamma curve to the power of γ equals the output value of the cyan encoding curve; and γ as it works out equals 0.4545

V_I 0 = V_O 0
V_I 0.25 = V_O 0.532
V_I 0.50 = V_O 0.729
V_I 0.75 = V_O 0.878
V_I 1.0 = V_O 1.0

Now isn’t that bit of maths sexy………………..yeah!

Basically the gamma encoding process remaps all the tones in the image and redistributes them in a non-linear ratio which is more familiar to our eye.

Note: the gamma of human vision is not really gamma 1/2.2 – gamma 0.4545. It would be near impossible to actually quantify gamma for our eye due to the behavior of the iris etc, but to all intents and purposes modern photographic principles regard it as being ‘similar to’..

So the story so far equates to this:

Gamma encoding redistributes tones in a non-linear manner.

But things are never quite so straight forward are they…?

Firstly, if gamma < 1 (less than 1) the encoding curve goes upwards – as does the cyan curve in the graph above.

But if gamma > 1 (greater than 1) the curve goes downwards.

A calibrated monitor has (or should have) a calibrated device gamma of 2.2:

Linear, Encoding & Monitor gamma curves.

As you can now see, the monitor device gamma of 2.2 is the opposite of the encoding gamma – after all, the latter is the reciprocal of the former.

So what happens when we apply the decoding gamma/monitor gamma of 2.2 to our gamma encoded image?

The net effect of Encode & Decode gamma – Linear.

That’s right, we end up back where we started!

Now, are you thinking:

Don’t understand?
We are back with our super dark image again?

Welcome to the worlds biggest Bear-Trap!

The “Learning Gamma Bear Trap”

Hands up those who are thinking this is what happens:

If your arm so much as twitched then you are not alone!

I’ll admit to being naughty and leading you to edge of the pit containing the bear trap – but I didn’t push you!

While you’ve been reading this post have you noticed the occasional random bold and underlined text?

Them’s clues folks!

The super dark images – both seascape and the rope coil – are all “GAMMA 1.0 displayed on a GAMMA 2.2 device without any management”.

That doesn’t mean a gamma 1.0 RAW file actually LOOKS like that in it’s own gamma environment!

That’s the bear trap!

Gamma 1.0 to gamma 2.2 encoding and decoding

Our RAW file actually looks quite normal in its own gamma environment (2nd from left) – but look at the histogram and how all those darker mid tones and shadows are piled up to the left.

Gamma encoding to 1/2.2 (gamma 0.4545) redistributes and remaps those all the tones and lightens the image by pushing the curve up BUT leaves the black and white points where they are. No tones have been added or taken away, the operation just redistributes what’s already there. Check out the histogram.

Then the gamma decode operation takes place and we end up with the image on the right – looks perfect and ready for processing, but notice the histogram, we keep the encoding redistribution of tones.

So, are we back where we started? No.

Luckily for us gamma encoding and decoding is all fully automatic within a colour managed work flow and RAW handlers such as Lightroom, ACR and CapOnePro etc.

Image gamma changes are required when an image is moved from one RGB colour space to another:

ProPhoto RGB has a gamma of 1.8
Adobe RGB 1998 has a gamma of 2.2
sRGB has an oddball gamma that equates to an average of 2.2 but is nearly 1.8 in the deep shadow tones.
Lightrooms working colour space is ProPhoto linear, in other words gamma 1.0
Lightrooms viewing space is MelissaRGB which equates to Prophoto with an sRGB gamma.

Image gamma changes need to occur when images are sent to a desktop printer – the encode/decode characteristics are actually part and parcel of the printer profile information.

Gamma awareness should be exercised when it comes to monitors:

Most plug & play monitors are set to far too high a gamma ‘out the box’ – get it calibrated properly ASAP; it’s not just about colour accuracy.
Laptop screen gamma changes with viewing position – God they are awful!

Anyway, that just about wraps up this brief explanation of gamma; believe me it is brief and somewhat simplified – but hopefully you get the picture!

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Photoshop CC Update

Posted on January 16, 2014 by Andrew Astbury

Photoshop CC Update

Installing a new Photoshop CC update is supposed to be a simple matter of clicking a button and the job gets done.

This morning both my Mac systems were telling me to update from v14.1.2 to v14.2

I have two Macs, a late 2012 iMac and a mid 2009 Mac Pro. The Mac Pro used to run Snow Leopard but was upgraded to Mountain Lion because of Lightroom 5 dropping Snow Leopard support.

Now I never have any problems with Cloud Updates from Adobe on the iMac, but sometimes the Mac Pro can do some strange things – and this morning was no exception!

The update installed on the iMac without a hitch, but when the update was complete on the Mac Pro I was greeted with a message telling me that some components had not installed correctly. On opening Photoshop CC I was greeted with the fact that the version had rolled back to v14.0 and that hitting UPDATE in both the app and my CC control panel simply informed me that my software was up to date and no updates were available!

So I just thought I’d do a blog entry on what to do if this ever happens to you!

Remove Photoshop CC

The first thing to do is UNINSTALL Photoshop CC with the supplied uninstaller.

You’ll find this in the main Photoshop CC root directory:

Locate the Photoshop CC Uninstaller.

Take my advice and put a tick in the check box to “Remove Preferences” – the Photoshop preferences file can be a royal pain in the ass sometimes, so dump it – a new one will get written as soon as your fire Photoshop up after the new install.

Click UNINSTALL.

Once this action is complete YOU MUST RESTART THE MACHINE.

After the restart wait for the Creative Cloud to connect then open your CC control panel.

Under the Apps tab you’ll see that Photoshop CC is no longer listed.

Scroll down past all the apps Adobe have listed and you’ll come to Photoshop CC; it’ll have an INSTALL button next to it – click the install button:

Install Photoshop CC from the Cloud control panel.

If you are installing the 14.1.2 to 14.2 update (the current one as of today’s date) you might find a couple of long ‘stick bits’ during the installation process – notably between 1 and 20% and a long one at 90% – just let the machine do it’s thing.

When the update is complete I’d recommend you do a restart – it might not be necessary, but I do it anyway.

Once the machine has restarted fire up Photoshop, click on ‘About Photoshop’ and you should see:

Photoshop “about screen” showing version number.

Because we dumped the preferences file we need to go and change the defaults for best best working practice:

Preferences Interface tab.

If you want to change the BG colour then do it here.

Next, click File Handling:

File handling tab in Photoshop Preferences

Remove the tick from the SAVE IN BACKGROUND check box – like the person who put it there, you too might think background auto-save is a good idea – IT ISN’T – think about it!

Finally, go to Performance:

Photoshop preferences Performance tab

and change the Scratch Disc to somewhere other than your system drive if you have the internal drives fitted. If you only have 1 internal drive then leave “as is”. You ‘could’ use an external drive as a scratch disk, but to be honest it really does need to be a fast drive over a fast connection – USB 2 to an old 250Gb portable isn’t really going to cut it!

You can go and check your Colour Settings, though these should not have changed – assuming you had ’em set right in the first place!

Here’s what they SHOULD look like:

Photoshop PROPER COLOUR SETTINGS!

That’s it – you’re done!

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Andy Astburys' Photography Blog

A general photography blog

Category Archives: Adobe Photoshop

Image Retouching

Image Retouching in Photoshop CC 2014

Lumenzia for Wildlife

The Lumenzia Photoshop extension

Colour Editing in Photoshop

Colour Editing in Photoshop using the Channel Mixer

Lumenzia – Not Just for Landscapes

Lumenzia for Easy Luminosity Masking

Lumenzia for Easy Luminosity Masking..

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Camera Calibration

Custom Camera Calibration

Parallel Horizontals.

Quite often when shooting landscapes, or more commonly seascapes, you may run into a problem with parallel horizontals and distortion between far and near horizontal features such as in the image below.

Paper White – Desktop Printing 101

Paper White video

Gamma Encoding – Under the Hood

Gamma, Gamma Encoding & Decoding

What is Gamma?

RAW file Gamma

The “Learning Gamma Bear Trap”

Photoshop CC Update

Photoshop CC Update

Remove Photoshop CC

Please consider supporting this blog.

Image Retouching in Photoshop CC 2014

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The Lumenzia Photoshop extension

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Colour Editing in Photoshop using the Channel Mixer

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Lumenzia for Easy Luminosity Masking..

Please consider supporting this blog.

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Custom Camera Calibration

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Quite often when shooting landscapes, or more commonly seascapes, you may run into a problem with parallel horizontals and distortion between far and near horizontal features such as in the image below.

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Paper White video

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Gamma, Gamma Encoding & Decoding

What is Gamma?

RAW file Gamma

The “Learning Gamma Bear Trap”

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Photoshop CC Update

Remove Photoshop CC

Please consider supporting this blog.

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