iEXPOSURE give you combination of apertures and shutter speed for the given exposure value (EV) and film speed
Apperture priority mode
Shutter priority mode
EV value chart
Relationship between EV, foot-candles and LUX

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Knowledge of Exposure Value can significantly enhance your ability as a photographer.
If you want to control the creative side of photography, you need to understand the interrelationship of Exposure Value, film speed, aperture and shutter speed.
Photography exposure value calculator give you combination of apertures and shutter speed for the given exposure value (EV) and film speed.
In order to be useful, Exposure Value number must be converted into an f/stop and shutter speed combination that will provide the proper exposure for the film speed you have chosen. Within each factor, as you move from one number to the next, the amount of light is either doubled or halved.