Hmm I have tried watermarking and fell foul of problems if the images were too small after watermarking a file and then trying to reduce the same image as a thumb common practice for many of us here.. The Canon data verification may be worth looking at if you have a lot of images that you want to protect if you are a Canon user but is rather expensive. There is a new version to cover less Pro spec cameras DVK-E2 Like its predecessor, this kit can verify whether or not a photo is an untouched original. But its use of a Secure Mobile (SM) card reader, instead of an IC card reader, makes it more compact than the previous version. Moreover, the versatile DVK-E2 is able to verify images photographed by the EOS-1Ds as long as they are appended with a data verification image and will work with the 20D

Danny O'Byrne  http://www.digitalartzone.co.uk/

"All the technique in the world doesn't compensate for the inability to notice" Eliott Erwitt