As LostPatrol says..."you shouldnt re-save an original Jpeg, as every time you do that it degrades the image, as it uses compression." If you modify your out of the cam JPEG with image editing software, then save it again as a JPEG....even with a new file name, you will degrade your image as you are compressing an already compressed image. Each time you re-JPEG, some information is discarded. Similar to making a photocopy of a photocopy of a photocopy... Precisely the reason to shoot in RAW mode as per the thread from a few days ago.....unless of course you can get your image bang on right out of the camera and don't need further processing.

In youth, we learn....with age, we understand.