We pose and answer questions about differences between sRGB and ARGB color spaces as if they are easily answered and intuitively obvious. Jesper's answer is all you really need to know – or is it . . .
For those who continue to care about the difference between Adobe RGB (ARGB) and sRGB, keep reading . . .
In RGB color spaces, a color is defineed with 3 numbers, e.g. R=230, G=20, B=20.
Each RGB color space is defined, in part, by the actual color of its Red, Green, and Blue primaries. R=230 means 230/256 of the Red primary. The colors of the primaries are specified in a well-defined reference color space. ARGB and sRGB have the same Red and Blue primaries, but different Green primaries. You can think of these 3 primaries as forming a triangular boundary that contains all colors in the space.
A color number triplet is meaningless until it is ASSIGNED to a color space. Only then can you know what the actual color is.
We can CONVERT the color numbers of one color space to the exact or near approximation of the same color in another space. Thus:
- R=250, G=230, B=70 in sRGB equals R=244, G=229, B=86 in ARGB
- R=255 in sRGB equals R=219 in ARGB, with G=B=0 for both.
After conversion from one color space to another, the image will likely look the same on most CRT monitors in a color managed application (e.g. Photoshop). However, in non color managed environments (the web), they may look very different.
The larger gamut ARGB color space has colors that cannot be displayed on most CRT monitors since their phosphors are calibrated to display the sRGB color space (approximately). Thus it is usually not possible to tell the difference between an sRGB and ARGB image when working in a color managed application which handles the assigned color space properly.
Take home messages/implications:
-ARGB images which have not been converted to sRGB color space will appear flat and desaturated when viewed in non color managed environments (the web).
-ARGB images when converted to sRGB for web viewing will look fine.
-sRGB images will look fine in PS and on the web.
-sRGB viewed in Photoshop but mistakenly assigned to ARGB will look more vibrant.
IMO – it takes quite a bit of effort to understand why the above statements are true.
The tide is shifting quite strongly towards the universal adoption of sRGB as a common denominator color space for image editing and viewing. Whether this is good or bad opens an argument that will not end in our lifetime. 