This is the "emacs of image editors". It has a small footprint and a simple interface with a lot of neat shortcuts that leaves screen space for the important thing: The images! The interface is optimized for requiring as few clicks and keys as possible for a typical work flow in editing photos, writing papers, powerpoints, and documents, and testing new image processing algorithms. Now in version 2 you can even develop RAW images from most cameras (tested with Canon and Nikon) - you can get even change the settings! It has a lot of other powerful features like blending, retouching, lens distortion, filtering, 3D reconstruction, etc. right at your fingertips.