Image tuning photographs of documents

I have been pleasantly surprised at how effective image processing can be for making photographs of documents more readable. The best program in the 602Software suite, in my opinion, is 602Photo. I am using that to process copies of photographs from the Nationaal Archief, in The Hague. Right now, I am processing photographs of handwritten documents from 1652, all relating to the Dutch navy, fleet, ships, and naval officers. The photographs all have a green tinge, for some reason. I am cropping the black background, making them easier to print, doing "image tuning", and adjusting brightness and contrast. One new thing that I am doing is adjusting "color channels". I can make the pages in the image look more like the actual document. I have been helped by my visit to the Nationaal Archief, back on 8 May 2007 with Carl Stapel, where I was able to see and handle some of the actual pages.