EV / Exposure Value

Exposure Value numbers are a shorthand substitute for the shutter speed/aperture combination, using a single number instead of two. Each EV number represents any of many different but equivalent combinations of aperture and shutter speed that will provide the same exposure (it might help to think of EV as Equivalent Value). The EV unit is equal to one stop.

It is important to note that although all camera settings with the same exposure value give the same exposure, they do not necessarily give the same picture. The shutter speed determines the amount of motion blur, and the relative aperture determines the depth-of-field.

1 second at F1.0 equals EV0; all other EV numbers are defined with respect to this definition.