Exposure Value
Exposure value (EV) is a single number that combines aperture and shutter speed into one measure of total light reaching the sensor, conventionally referenced to ISO 100. Every whole step up in EV represents exactly one stop less light; every step down represents one stop more, the identical doubling-and-halving relationship every exposure variable shares.
EV is most useful as a shorthand for comparing or matching exposures without listing every individual setting — two completely different combinations of aperture and shutter speed that share the same EV at the same ISO produce identical image brightness, even though the resulting depth of field and motion rendering can look completely different.
Frequently Asked Questions
What EV does the classic Sunny 16 rule correspond to?
Roughly EV 14-15 at ISO 100, the reference brightness of direct, bright sunlight that f/16 and a shutter speed close to 1 over the ISO number is calibrated to expose correctly.
Does EV account for ISO at all?
The base EV figure is defined at ISO 100 by convention, but photographers commonly speak of an 'EV at a given ISO,' which shifts the effective brightness represented by each EV value — always check which convention a specific source is using before comparing numbers directly.