Colour space and device profiles seem to cause a certain degree of confusion for a lot of people; and a feeling of dread, panic and total fear in others!
The reality of colour spaces and device profiles is that they are really simple things, and that how and why we use them in a colour managed work flow is perfectly logical and easy to understand.
Up to a point colour spaces and device profiles are one and the same thing – they define a certain “volume” of colours from red to green to blue, and from black to white – and all the colours that lie in between those five points.
The colour spaces that most photographers are by now familiar with are ProPhotoRGB, AdobeRGB(1998) and sRGB – these are classed as “working colour spaces” and are standards of colour set by the International Color Consortium, or ICC; and they all have one thing in common; where red, green and blue are present in equal amounts the colour produced will be NEUTRAL.
The only real differences between these three working colour spaces is the “distances” between the five set points of red, green, blue, black and white. The greater the distance between the three primary colours then the greater is the degree of graduation between them, hence the greater the number of potential colours. In the diagram below we can see the sRGB & ProPhoto working colour spaces displayed on the same axes:
If we were to mark five different points on the surface of a partially inflated balloon, and then inflate it some more then the points in relation to the balloons surface would NOT change: the points remain the same. But the spatial distances between the points would change, as would the internal volume. It’s the same with our five points of colour reference – red, green, blue, black & white – they do NOT change between colour spaces; red is red no matter what the working colour space. But the range of potential colours between our 5 points of reference increases due to increased colour space volume.
So now we have dealt with the basics of the three main working colour spaces, we need to consider the volume of colour our camera sensor can capture – if you like, its colour space; but I’d rather use the word “gamut”.
Let’s take the Canon 5DMk3 as an example, and look at the volume, or gamut, of colour that its sensor can capture, in direct comparison with our 3 quantifiable working colour spaces:
In a previous blog article I wrote – see here – I mentioned how to setup the colour settings in Photoshop, and this is why. If you want to keep the greatest proportion of your camera sensors captured colour then you need to contain the image within the ProPhotoRGB working colour space. If you don’t, and you use AdobeRGB or sRGB as Photoshops working colour space then you will loose a certain proportion of those captured colours – as I’ve heard it put before, it’s like a sex change operation – certain colours get chopped off, and once that’s happened you can’t get them back!
To keep things really simple just think of the 3 standard working colour spaces as buckets – the bigger the bucket, the more colour it contains; and you can’t tip the colours captured by your camera into a smaller bucket without getting spillage and making a mess on the floor!
As I said before, working colour spaces are neutral; but seldom does our camera ever capture a scene that contains pure neutrals. Even though an item in the scene may well be neutral in colour, camera sensors quite often skew these colours ever so slightly; most Canon RAW files always look a teeny-weeny ever so slight bit magenta to me when I import them; but there again I’m a Nikon shooter seem to have a minute greenish tinge to them before processing.
Throughout our imaging work flow we have 3 stages:
1. Input (camera or scanner).
2. Working Process (Lightroom, Photoshop etc).
3. Output (printer for example).
And each stage has its representative type of colour space – we have input profiles, working colour spaces and output profiles.
So we have our camera capture gamut (colour space if you like) and we’ve opened our image in Photoshop or Lightroom in the ProPhoto working colour space – there’s NO SPILLAGE!
We now come to the crux of colour management; before we can do anything else we need to profile our “window onto our image” – the monitor.
In order to see the reality of what the camera captured we need to ensure that our monitor is in line with our WORKING COLOUR SPACE in terms of colour neutrality – not that of the camera as some people seem to think.
All 3 working colour spaces posses the same degree of colour neutrality where red, green & blue are present at the same values irrespective of physical size of the colour space.
So as long as our monitor is profiled to be:
1. Accurately COLOUR NEUTRAL
2. Displaying maximum brightness only in the presence true white – which you’ll hardly ever photograph, even snow isn’t white.
then we will see a highly workable representation of image colour neutrality and luminosity on our monitor. Only by working this way can we actually tell if the camera has captured the image correctly in terms of colour balance and overall exposure.
And the fact that our monitor CANNOT display all the colours contained within our big ProPhoto bucket is, to all intents and purposes, a fairly mute point; though seeing as many of them as possible is never a bad thing.
And using a monitor that does NOT display the volume of colour approximating or exceeding that of the Adobe working space can be highly detrimental for the reasons discussed in my previous post.
Now that we’ve covered input profiles and working colour spaces we need to move on and outline the basics of output profiles, and printer profiles in particular.
In the image above we can see both the Adobe and sRGB working spaces and the full distribution of colours contained in the Kingfisher image which is a TIFF file in our big ProPhoto bucket of colour; and a black trace which is the colour profile (or space if you like) for Permajet Oyster paper using Epson UltraChrome HDR ink on an Epson 7900 printer.
As we can see, some of the colours contained in the image fall outside the gamut of the sRGB working colour space; notably some oranges and “electric blues” which are basically colours of the subject and are most critical to keep in the print.
However, all those ProPhoto colours are capable of being reproduced on the Epson 7900 using Permajet Oyster paper because, as the black trace shows, the printer/ink/paper combination can reproduce colours that lie outside of the Adobe working colour space.
The whole purpose of that particular profile is to ensure that the print matches what we can see on the monitor both in terms of colour and brightness – in other words, what we see is what we get – WYSIWYG!
The beauty of a colour managed workflow is that it’s economical – assuming the image is processed correctly then printing via an accurate printer profile can give you a perfect printed rendition of your screen image using just a single sheet of paper – and only one sheets worth of ink.
If we were to switch printers to an Epson 3000 using UltraChrome K3 ink on the very same paper, the area circled in white shows us that there are a couple of orange hue colours that are a little problematic – they lie either close to or outside the colour gamut of this printer/ink/paper combination, and so they need to be changed in order to ‘fit’, either by localised adjustment or variation of rendering intent – but that’s a story for later!
Why is it different? Well, it’s not to do with the paper for sure, so it’s down to either the ink change or printer head. Using the same K3 ink in an Epson 4800 brings the colours back into gamut, so the difference is in the printer head itself, or the printer driver, but as I said, it’s a small problem easily fixed.
When you consider the low cost of achieving an accurate monitor profile – see this previous post – and combine that with an accurate printer output profile or two to match your chosen printer papers, and then deploy these assets correctly you have a proper colour managed workflow. Add to that the cost savings in ink and paper and it becomes a bit of a “no-brainer” doesn’t it?
In this post I set out to hopefully ‘demystify’ colour spaces and profiles in terms of what they are and how they are used – I hope I’ve succeeded!
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