How to do color correction for scanned photos?

April 3, 2005 5:41 PM

I've got several scanned photographs that have large sections near the edge of the image that have been tinted red (as seems to be somewhat common with cheap cameras/film) How can I fix these areas of the image to match the rest in color?

I'm trying to do this in the Gimp (2.0.5) on WindowsXP. The only other tool I have is Adobe Photoshop Album, which just has kind of a generic "fix all" color correction that will only do the whole image at once and not parts as I need. I've been playing around with the "Curves" color tool on those affected areas and I'm guessing that's probably the way to go in general but I can't seem to get it right without overcorrecting so that even though I reduce the red in those areas, they still don't match up with the rest of the image. Does anyone have any tricks for this kind of thing, or better yet know of a filter that is specifically for something like this?

posted by shinji_ikari to computers & internet (5 comments total)

You're on the right track using curves. But you should be selecting just the afflicted area (use the lasso tool and then feather the selection 3 or so pixels), and then adjusting just the red channel (select it from the dropdown that has "rgb" as the default).

After that, it's really just a question of playing with the points in the curve tool to get the desired effect. If your results aren't satisfactory, look into using the "replace color" option and the "color balance" adjustment.
posted by Mayor Curley at 6:19 PM on April 3, 2005

If the tinting seems to be regular, then you might get a more accurate result using a gradient mask rather than lassoing the selection.

Don't know if either GIMP/PsElements has masking capabilities, though.
posted by blag at 6:54 PM on April 3, 2005

If the tinting seems to be regular, then you might get a more accurate result using a gradient mask rather than lassoing the selection.

GIMP does has adequate masking, but we're keeping it simple, remember?
posted by Mayor Curley at 7:22 PM on April 3, 2005

Yeah, the tricky part is that the tinting is kind of blotchy rather than uniform so if I lasso the whole affected area, the less tinted spots start to look funny by the time I've lowered the red channel enough for the more tinted regions. If I try to break up the tinted areas and do each separately, I run into the problem of matching the colors of each of those areas to each other and the rest of the image. Otherwise it looks very obviously edited as there are many areas that are closer to normal in tone, but slightly off from each other.
posted by shinji_ikari at 5:33 AM on April 4, 2005

There's no perfect way to do this. Patience is part of it. Consider selecting by color, and then using the lasso to de-select the portions in the acceptable part of the photo that also get selected.

Getting the best strength for the selection will be trial-and-error. Obviously, use the highest res scan you can get.
posted by Mayor Curley at 6:32 AM on April 4, 2005