Disparai — Camera Exposure and Sunny 16 | disparai.com
A table of lighting conditions with their exposure value at ISO 100, and the equivalent aperture-shutter pairs from EV 0 upward.
Exposure value combines aperture and shutter speed in one number: EV equals the aperture value plus the time value. EV 0 corresponds to an exposure time of 1 second and an aperture of f/1.0. Every other value is built from that reference by powers of two, so each step of EV is exactly one stop, a factor of two in light.
The EV table for ISO 100 places a typical scene in full or slightly hazy sunlight at EV 15. Light sand or snow in the same light, with distinct shadows, sits at EV 16. The one-stop difference is the extra reflectance of the bright surface: the meter sees more light, so the exposure value is higher.
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Because the exposure of a scene can be achieved with many combinations of aperture and shutter speed that admit the same amount of light, each EV entry can be met by several pairs. EV 15 is f/16 at 1/100 s, or f/11 at 1/50 s, or f/8 at 1/25 s. EV 16 is f/16 at 1/125 s, or f/11 at 1/60 s, or f/8 at 1/30 s.
Below EV 10 the light is dim enough that shutter speeds drop into the range where camera shake becomes visible: hand-held work is usually limited to about 1/30 s or slower, so wide apertures and higher ISOs are needed. Above EV 16, in snow under a clear sky, the same aperture-shutter pairs shift one stop toward faster shutters or smaller apertures.
A camera's light meter measures the luminance of the scene and indicates the exposure settings. Reading the EV table alongside the meter tells you whether the meter is being fooled by backlight, by snow, or by a dark background, and which correction to apply.
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