Various standard operations you do on jpeg photos involve a loss in image quality.
In most programs, rotation, flipping, cropping and downscaling involve re-compressing the image, which always deteriorates image quality, even with the quality setting set to 100%.
If you like it clean, this free program allows these operations to occur without any re-encoding process, hence, without quality loss: http://jpegclub.org/ Look for jpeg-crop downwards.
thanks jpegclub!
