JPEG is a “lossy” compression algorithm

Friends don't let friends shoot JPG. At least shoot RAW plus JPG! Lisa

http://www.petapixel.com/2012/08/14/why-you-should-always-rotate-original-jpeg-photos-losslessly/

"JPEG is a “lossy” compression algorithm that’s geared towards storing and sharing photos without taking up too much disk space. Rotating these compressed images is usually done by decompressing, rotating, and then re-compressing. Since the re-compression is lossy (i.e. data is thrown away), this process results in slightly degraded photos (hence that warning)."


If you’re not convinced, check out this interesting experiment done by a Wikipedia user named Burny. Using a simple computer script, he took the following image and rotated it lossily 2000 times:

Here’s hows the image degraded through those 2000 rotations:




Pretty crazy, huh?

http://www.petapixel.com/2012/08/14/why-you-should-always-rotate-original-jpeg-photos-losslessly/