Pascal de Bruijn wrote:
Hi, I've more or less asked about this in the past, but I gave up on it, back then... I have two images of an IT8 chart... 1. A digital camera generated JPG (white-balanced, and gamma corrected) 2. A RAW file, converted to JPG (white-balanced, but not gamma corrected, so it's linear RGB) Both images, are in fact, the same image, just stored in a different way... I'd like to generate a profile, which would turn my nr 2 image into something very close to my nr 1 image. Is this possible? Can anybody help me with accomplishing this?
If the only difference between the images is actually the gamma, you won't need a profile -- a simple curve (e.g as adjustment layer in Photoshop) will do it. The shape of the curve is y = x^gamma where x and y are the RGB source and target values scaled to [0 ... 1].
Also the middle control in Photoshop's Levels Adjustment (Layers) is nothing but a gamma correction control.
If you have a matrix profile for one of the images, you can build one for the counterpart in Photoshop: Go to the Color Preferences and load the profile as your RGB working space, then select "Custom RGB" as your RGB working space. Photoshop will show you a dialog with the gamma, whitepoint and primary values of the profile. You can edit the gamma value and save this modified "Custom RGB" setting as ICC profile. (Don't forget to return to your original Color settings when you are done.
Klaus
