Using The GIMP (or Photoshop) to Improve Photos?

Nom du Keyboard asks: "Is it possible to use The GIMP (or Photoshop) to improve my digital photos? I have a mid-range 7.1MP Olympus camera capable of shooting in Raw mode. When I inspected a section of clear blue sky on a bright, sunny day (which I've long believed to be relatively good reference of uniform color and brightness) I was surprised (disappointed, since I expect digital perfection) at the variance in adjacent pixels. It's also a quick way to identify any bad pixels. Surprisingly, actual photos from this camera look pretty good despite this variance so far. Moving on from that point it led me to wonder that, if you shot a uniform white surface, perhaps blurred as much as possible to avoid any imperfections in the surface itself, could a correction (adjustment) layer be created in GIMP or Photoshop exactly tuned to your camera that fixed the variations in your CCD sensor and improved the image quality in the process. Any thoughts?"

Comments

Yes.

[oskard]

If we saw a sample of the photos, it would be easy to determine if they could be fixed. Its hard to understand what the exact problem is from a text description, but the general answer is: Yes, anything can be done with The GIMP / PS.

Or GREYCstoration

[dschl]

GREYCstoration. Ugly name, but does the same job, and is open source. Haven't tried it, but there appear to be several plugins for various open source digicam programs and image editors (bottom of their downloads page).

Re:Yes Exactly! Only Backwards....

[hankwang]

Then you add that as a layer in photoshop, subtract it from the real image, and the non-random noise disappears.

I doubt that that will work. Once in the computer, the pixel values are not proportional to the absolute brightness, see gamma correction on wikipedia. You would need to do the substraction on linearly encoded data (12 or more bits rather than 8). Maybe photoshop can indeed do this, provided you find the right settings, but GIMP as far as I know doesn't.