You cannot change the filename in-camera; the first characters are designed to be unique to the camera. This is useful when identifying stolen goods, and a necessity when a team of photographers is covering an event (like the Super Bowl) and is highly unlikely ever to be changed. Learn to use Photoshop's batch rename function.

I rename all my files anyway (I typically shoot with 2 bodies) and therefore don't care what the camera prefix is, as long as it isn't FU**

Sorry to bother you folks, but I have a question. With the 1DmkII ,Is there a way to change the image file name within the camera? On my new 1D the image name is LYOUXXXX rather then the standard IMG as in my 10D. From what I have read this is a unique identifier programed by the factory and each camera is different. Can it be changed? I know I can add file folders onto the mem card or change folder names, but have found nowhere where I can change the actual image file name....

Thanks in advance..

Thanks Jonathan. I'm not real crazy the designated letters ( LYOU XXXX ), but they won't be hard to remember anyway.. I agree with you about being a good feature for theft recovery or in instances where there are files from more then one camera....

Thanks for your reply...