Exposure (photography)
lastmod 2026-02-22created 2026-02-221 edits
In photography, exposure is the amount of light per unit area reaching a frame of photographic film or the surface of an electronic image sensor. It is determined by exposure time, lens f-number, and scene luminance. Exposure is measured in the unit lux-seconds (symbol lx⋅s) and can be calculated from the exposure value (EV) and scene luminance in a specified region.
An "exposure" is a single shutter cycle. For example, a long exposure refers to a single, long shutter cycle to gather enough dim light, whereas a multiple exposure involves a series of shutter cycles, effectively layering a series of photographs in one image. The accumulated photometric exposure (Hv) is the same as long as the total exposure time is the same.
See also
- Photography
- Camera
- Metering