Gimp is an image processing software package that is akin to Photoshop,as it were, but I don't believe it is as good as Photoshop.
You will have to just drag an image or two into the Gimp and try out levels and curves and see how the work. Scratch around on the 'net for articles related to processing, there are many to choose from.
By the way, is there Mac driver for the DSI range of cameras, how did you get on with that?
Good info to have for others.
Nebulosity has an image processing side to it as well that you could play with, however, I don't use it.
