wghall29

I always shoot raw! It keeps all your options open.

f8lee Loc: New Mexico

I'm not certain about PNG files, but TIFF files do not use a "lossy" compression format like JPEG does. Every time it is saved, JPEG image files compressed by essentially removing redundant data - say a large field of blue is in the image; the JPEG might just denote "this color blue" for "this area" rather than proscribing a specific color for each pixel (that's the essence of it, anyway). It's for that reason that you can specify how high a quality you want to be. It is also the reason that with each new save process, the image will get a bit degraded.

Go ahead, take a JPEG image, open it in Photoshop (or anything) and without doing any actual alterations just save it as a new file (with a new name). Then open and save that one, and so forth. You will eventually see how the 5th or 10th or whatever generation is worse than the original.

Just opening a JPEG to view it and closing the window without making the save command does not invoke the compression algorithm, so you can do that as often as you like.