Practice question · Select all that apply
Which are true of the reciprocity law and its failure?
Hints
- Three describe the law and its limits; one extends a film defect to a different technology.
- Long digital exposures have a different problem entirely.
Show the answer
- B. Exposure is illuminance multiplied by time, so halving one and doubling the other should be equivalent
- C. The size of the departure differs from emulsion to emulsion and is published per film
- D. Film departs from the law at very long and very short exposures
Why
Sensors do not lose reciprocity, they accumulate thermal noise over long exposures instead, which looks bad for an unrelated reason. The third statement is the practical one: there is no universal correction, only the manufacturer's figures for the emulsion in the camera.
Practise Aperture, Shutter and Sensitivity
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