Recent events and some past on another forum got me to thinking about just how would one go about providing proof of copyright infringement. I suggest that there is no question a pro must submit originals to their respective copyright agencies using the strictest guidelines as a starter. In the U.S. this brings even more penalties to bear if the case is proven. On another forum there was much discussion about watermarking and even using staged props (certainly not always possible) to provide 'proof' of authorship. Watermarks can be fairly easy to remove so they are not really a deterrent to a determined effort. I came up with a cheesy method that embeds a watermark that is not visible. This watermark can be recovered even after the marked photo is manipulated buy such things as white balance ,etc. For best results one must try to 'match' and undo color temp corrections and reverse geometric transformations. At a certain level of black level cropping my method fails. Pretty simple to make a watermark image (MS Paint was used here). Modify the intensity to a level just barely above the target image black level. Then add the scaled image to the target image to produce a marked image. I've also adjusted the color temperature from the original to demonstrate how the watermark can be recovered. This is the suspect image. The original image (even with no adjustment in color temperature) Is subtracted from the suspect image producing the result The watermark is barely visible and impossible to have been placed or detected by the copyright violator! No matter who has the raw images if the once invisible watermark is revealed there are some pointed questions to be answered. Anyway, curious question about proof.