Design Nomenclature / Light & Optics
Exposure
Also called EV, exposure value
This entry has not been translated yet and is shown in English.
Strictly, the illuminance on the sensor multiplied by the time it is collected — lux-seconds, set by aperture and shutter alone. It determines how much light was actually recorded; ISO merely scales what gets done with the result afterwards.
In practice
One word, three jobs: a camera setting, a renderer's EV parameter mapping scene luminance to output, and a post slider that multiplies pixels after the fact. Only the first records anything.
Not to be confused with
- Tone mappingThe transform fitting a scene's luminance range into what a display can show — compressing highlights, holding mid-tone contrast, and deciding where things clip. It is neither a colour correction nor optional: some curve is always applied, and choosing none means choosing a hard clip.
- Dynamic rangeThe ratio between the largest and smallest luminance a scene, sensor, or display can carry, usually quoted in stops of doubling. A real scene may span twenty; a good sensor fourteen; an SDR display under ten. Everything difficult about photography lives in that gap.
- High keyA tonal strategy placing most of a scene's values in the upper register with a low key-to-fill ratio, so shadows stay open and transitions gentle. The range is compressed toward the light end deliberately: it is a decision about where the histogram sits, not a failure of exposure.