Diopter Optically, a unit of measurement of the refractive power of lenses. Refractive in this case, refers to the ability of the eye to bend light so that an image can be brought into focus. In photography, diopter is a term used to describe the focusing power of a supplementary or close up lens. The Nikon D-1 has a diopter that will adjust to the camera user's own eye, using a control button on the camera body viewfinder. This feature is used when a scene contains stark lighting contrasts or extremely bright or dimly lit subjects.
Exposure compensation is adjusted in increments called values.
Adjustment is made in values as small as one third value, with a range of plus 5 to minus 5 from the optimum exposure. This technique is also useful when shooting subjects in the shade on sunny days. In both examples, by exposing for the bright areas of a scene, and using the flash to fill in the darker shadows or foreground, a more pleasing balance of light is created. For example, the difference in sensitivity between 100 speed film and 400 speed film is equal to two full stops of exposure. Gain On the Canon GL-1 camcorder, gain is another exposure variable like aperture or shutter speed that refers to the camcorders exposure sensitivity range.