The single most important image processing function is known as stretching. In its simplest form, stretching is the same as adjusting the brightness and contrast of your television. Your television has these controls because it cannot display the world as it really is. Unlike your eyes, which can work on a sunny day or a moonless night, a television can handle only a very limited range of brightness. The huge dynamic range of the eye has never been duplicated by video display technology.
While video displays and printers still suffer from this severe limitation, the cameras do not. Modern high-performance CCD cameras can record up to 65,536 different brightness levels, yet most computer monitors can only display about 64 brightness levels (even if more levels are available, they usually cannot be distinguished on the monitor). This huge gap can be bridged using stretching techniques.
MaxIm DL has both "screen stretch" and permanent stretch capabilities. Screen stretch operations do not change the image; rather they adjust the way it is displayed. Screen stretch operations can be made ”permanent” so that the image can be exported to other software. More complex stretch functions attempt to adjust to reduce the dynamic range of images so features at very different brightness levels can be seen at the same time.