When I press the print screen button in Windows Xp and paste the clipboard in a new document in photoshop, the RGB values change quite a bit.
For instance, the gray background of photoshop (128,128,128) becomes slightly yellowish (125,126,120) !
Can anyone give me a clue about what I'm doing wrong ? Thanks.
Nothing, actually. Photoshop is color managed, which means that it doesn't give a s%#t about RGB numbers per se
, it cares about the actual color those numbers represent. So it's NOT sending the monitor "128,128,128", it's sending your monitor "50% gray, as determined by your monitor profile". In your case, that happens to be 125,126,120.
In any color managed application, the RGB numbers sent to the monitor or printer or any other output device WILL NOT be the same as the RGB numbers contained in the image data, because no two devices will display the exact same color when sent RGB 103,205,229, for example. What color management does is ensure that the RGB numbers sent to an output device (whether monitor, printer, or whatever) represent the SAME COLORS as in the original image file
. The actual RGB numbers sent to the device will depend on the profile for the device.