Tip of the day (Rgb VS srgb)

Now you might immediately think, as I did, that more colours must be a good thing so that must be the one to go for. Well unfortunately it’s not that simple. Having all those extra colours available is only of any use if the display medium can actually display those colours. And the bad news is, most can’t. Fire up Photoshop and load up a picture, pick something with lots of nice colours and some subtle hues, then make two copies of the picture with two different colour profiles. To change the colour profile you need to look under the edit menu, near the bottom you will see convert to profile… Set one version of the picture to sRGB and the other version to Adobe RGB (1998). Looking at the two pictures side by side in Photoshop you will see no difference at all. This is because Photoshop is making the necessary adjustments, based on the profile you have set, to display the colours correctly on your screen. Now close Photoshop and view your pictures in Windows Explorer or any other, non photo specific, software. You should see that the sRGB picture is much the same as you saw it in Photoshop and the Adobe RGB (1998) picture looks very dull in comparison. This is because most other software, including your web browser, defaults to sRGB, and is not able to display the extra colours in your Adobe 98 file. Looking back at the diagram above you can see that the brighter colours in the Adobe 98 picture would be cut off when displayed in an sRGB viewer, leaving you with the muddy colours in the middle range.

What about printing? Not all photos are destined for the web. What about printers? Sad to say that, unless you have a very high end specialist printer, the colour space will be about the same or maybe even smaller. Most printing houses recommend that you submit your files in sRGB and most inkjets, although they actually print in CMYK demand an sRGB input. Offset litho printing uses the CMYK colour space, as does all reproduction on paper, this colour space is even smaller than sRGB so a lot of rich blues and reds need to be re-calibrated before sending pictures to magazines. I produce a magazine with over a thousand photos in each edition and one of the biggest tasks just before going to press is changing the colour mode of all those photos to CMYK and tweaking each one manually to get the best tonal range.