Best duplicate checking program

Hello,
Can anyone recommend the best duplicate file checker program? I want to use it to find duplicates of image files, as through transferring files around I have inadvertently left copies of important pictures. However, I need to be very careful that I do not delete something that I want to keep, and image files can be saved in multiple compression formats. So I need a program that checks every file attribute and will tell me only when there are exact duplicates.
thank you.