The exposure value (also known as EV) is a number that represents a combination of a camera’s shutter speed and aperture, such that all combinations that yield the same exposure have the same EV value.
The EV concept was developed in an attempt to simplify choosing among combinations of equivalent camera settings, by the German shutter manufacturer Friedrich Deckel (de) in the 1950s.
Although all camera settings with the same EV nominally give the same exposure, they do not necessarily give the same picture. The aperture determines the depth of field, and the shutter-speed (exposure time) determines the amount of motion blur.
The table below is a good guide to use to determine the exposure value options.