[tlug] gimp: gamma adjust after the fact?

[Darren Cook <darren@example.com>]

When I scan a photo I can set the gamma value. For this particular image
it works fine on the preview, but not on the 1200 dpi full-size image;
it looks like it is either not applying the gamma adjust, or the
full-size image needs a higher value.

Not being a graphical designer, all I know about gamma is it is "the
knob you turn to make photos look good". Well, gimp has all these exotic
knobs but not the "make photos look good" knob. Does anyone know where
it is hidden, or what it is called, so I can use it on a photo already
scanned in. At the moment I'm enjoying a cycle of "scan, frown, adjust
(scanner) gamma, scan again, frown again, ..."

Darren

P.S. Google was no help as all the hits seem to be articles aimed at
graphic designers who actually want to play with exotic knobs.