Unshake is a free program which analyses photos which are blurred, poorly focused or shaken, and which uses the results to give clearer pictures. Most image processors offer pre-defined filters which have been found useful after a lot of use. They bring out hidden detail by emphasising changes (like edges) in pictures. Distinct from this, deconvolvers try to recover what the original scene looked like, but they have the problem that one needs to specify exactly how the picture was blurred in the first place (for example, if the camera was poorly focused, one would ideally specify not just how bad the focus was, but how fast the shutter moved at each phase of its cycle, and how many leaves the shutter had). An automatic deconvolver attempts to estimate itself how the picture was blurred in the first place, then to deduce what the original scene would have looked like. This is a very difficult task, involving automatically setting dozens or hundreds of controls.