I am using PS CS2.

I am attempting to colour correct a digital image.

Suppose you place a grey card in a position within the image you are taking with a digital camera. When you display this digital image in CS2 and sample the colour of the grey card you find that the R G and B are not equal as you could expect but rather only close to equal. As an example they may show:

R = 170 G = 168 and B = 172.

I will pick, let us say, the G = 168 and then attempt to modify for the whole image the R and the B also to 168 so that when I sample the grey card it now reads the same values for the three colours. I guess my question is how do you modify the colour of my whole image by a number, plus or minus, rather than the percentage figure that appears when you use IMAGE/ADJUSTMENTS.

This link may be helpful! http://www.webreference.com/graphics/column13/

Maybe post the image too .... give us an idea of what you see and are attempting.

I'm really late here but I hope this helps: You have to select the color area(s) with that grey (or have them on a layer of their own); then in the Colour-palette (from Window-menu) with RGB-sliders, adjust the numbers, then fill previous colour areas (with no feather!). I don't actually know any other ways to use exact colours in PS. Good luck with your work! :-)

you should choose image/adjustments/levels (or even better make a new levels adjustmentlayer). In the levels window you see three little eyedropper-buttons (under the ok, cancel, load, ... buttons) click the middle one and double click on the graycard in your image. this sets your graypoint. If you double click on the middle eyedropper you can even set your own target graypoint by the rgb numbers. same goes for the highlight and shadow eyedroppers...