File Format and Colourspace (Colorspace) Primer

For the past 10 years I have been giving lectures on digital imaging for photographic clubs in the South East of England. (25 years ago I was giving companies talks and training on Photoshop, scanning and multimedia!).

I am available – for a small fee – to travel to clubs in the South East and given any one of the talks listed in the menu. Please contact me for further information. My details are in the Surrey Photographic Association handbook.

This is an outline of the contents of the talk and a summary of the findings with before and after images to help those that have been to one of my lectures. When I give the talks I include many different demonstrations, these will help to serve as an aid to those who have seen the talk.

 

File Format and Colourspace (Colorspace) Primer

 

This is a short primer that I often cover in several of my talks, but I have separated it here for convenience.

File Formats Priner-1

File Formats Priner-5

File Formats Priner-2

File Formats Priner-3

File Formats Priner-4

 

 

Colourspaces in brief – Why Lightroom uses ProPhotoRGB and why you should too!

The colour range captured by a modern digital camera far exceeds the colour range of sRGB or Adobe RGB colorspaces. Digital SLR’s have a choice between the two in their menu systems, but THIS APPLIES ONLY TO JPEGS!!

When shooting raw files, there is no colour space. On import into Lightroom, the raw file is opened into the ProPhotoRGB colour space. When you look at the diagrams below  you can see why Adobe did this.

This diagram shows a comparison of all the visible colours – the outer curve with sRGB, AdobeRGB and ProPhotoRGB (ignore the others)

CIE1931xy_gamut_comparison.svg
By BenRG and cmglee – http://commons.wikimedia.org/wiki/File:CIE1931xy_blank.svg, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=32158329

We can look at this in more detail and in 3D, using Apple’s Colorsync utility ( See bottom or page for more details on how to do this yourself). This means I can compare the colour range of a camera with printers, screens etc and with these colorspaces.

The two images immediately below show the colour range of the Leica M9 vs the sRGB colorspace. sRGB is the colour range of the internet, not for cameras, printers or even screens. As you can see restricting your camera to shoot sRGB considerably reduces the range of colours available, particularly the greens (“Digital Green” anyone?)

Screen Shot 2016-02-21 at 16.15.07
Leica M9 (Transparent Grey) vs sRGB (in colour)
Screen Shot 2016-02-21 at 16.14.55
Leica M9 (Transparent Grey) vs sRGB (in colour)

Shooting in Adobe RGB improves the situation a little, but still not enough.

Screen Shot 2016-02-21 at 16.14.15
Leica M9 vs AdobeRGB (Coloured)
Screen Shot 2016-02-21 at 16.14.40
Leica M9 vs AdobeRGB (Coloured)

 

Interestingly, ProPhotoRGB was created by Kodak, specifically for DSLR’s. As you can see it is much closer – but not 100% aligned with the Leica M9 colorspace.

Screen Shot 2016-02-21 at 16.16.26
Colourspace Leica M9 (Grey transparent) vs ProphotoRGB (in colour)

 

Some people argue that because Printers and screens can’t display all of the ProPhotoRGB colour space , that it is better to work in one of the smaller space. But the problem is that the printer / parer combination and the screen are often able to print/display colours OUTSIDE the range of sRGB or Adobe RGB.

The safest solution then is to work in ProPhotoRGB and then convert to the appropriate printer/paper/ink profile at the end, previewing it on your monitor with a gamut warning in Photoshop. This approach leads to better colour accuracy and less damage to the original image.

Comparison of Adobe RGB (in colour) with Printer profile for Epson 3800 / Permajet Oyster semigloss paper. As you can see the correlation is not good! The sRGB version is a joke!

If you’ve been capturing jpegs and printing out colour pictures and wonder why you have been having so much trouble with unrealistic colours, now you know why!

sRGB should only be used for jpg output to the web – which is what it was designed for.

Screen Shot 2016-02-21 at 16.33.28
Adobe RGB (in colour) vs Epson 3800 printing Permajet Oyster
Screen Shot 2016-02-21 at 16.35.58
sRGB colourspace (in colour) compared to Epson 3800 Permajet Oyster Paper

 

And finally…

If, like me you use a Mac, you can play with these 3 dimensional colorspaces yourself using the Colorspace Utility – it will be in the “uitlities” folder within “Applications”.

Screen Shot 2016-02-21 at 16.40.40
Apple’s Colorsync Utility