Photographic Exposure: Measurement, Camera Control, and Exposure Latitude

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Photographic exposure

The amount of light per unit area that reaches film or an image sensor.

Radiant exposure ($H_e$)

Radiant energy received per unit area, measured in joules per square meter (J/m²).

Luminous exposure ($H_v$)

Illuminance multiplied by exposure duration; measured in lux-seconds (lx·s).

Long exposure versus multiple exposure

A long exposure uses one extended shutter cycle; a multiple exposure combines images from several cycles.

Log exposure in sensitometry

Exposure represented using the base-10 logarithm of $H$, written as $\log_{10}(H)$.

Quiz questions

1. In automatic exposure mode, what does the camera meter generally aim to do with a subject's mid-tone?Answer: Render it as a mid-tone in the photograph.
2. What exposure change does a compensation setting of +1 stop request relative to the meter's reference?Answer: Twice as much exposure.
3. In shutter-priority mode, which setting does the photographer choose directly?Answer: Shutter speed; the camera adjusts the aperture.
4. How can a graduated neutral-density filter help with a high-contrast scene?Answer: It reduces light from bright areas more than from darker areas.
5. What makes clipped digital highlights difficult or impossible to restore?Answer: The highlight detail may not have been recorded.