Photo-lab timer
Timer for enlarging in dark room
A photo-lab timer, photo interval timer, or darkroom timer is a timer used in photography for timing the process of projecting negatives to photosensitive paper with an enlarger, making photographic prints of them at any scale. It is a device which is attached to the photo lab enlarger to ensure that the duration of photo exposures on sensitive paper can be accurately timed. When the selected time has elapsed, the enlarger is switched off or an alarm is sounded, for the photographer to turn it off.
Initially they were conventional clocks, which were replaced by electromechanical timers, which were subsequently substituted entirely by electronic equipment.
Operation
After specifying the exposure time, the supply of power to the enlarger is activated by pushing a start button, thus timing the exposure exactly. The selectable time range is typically from 1/10th of a second to one or more minutes. Most exposure timers also have a continuous light switch, which is especially helpful for framing and focusing. Depending on the version, the desired duty cycle is set by means of a mechanical dial with scale or a push-button arrangement along with a numerical display. Some variants allow the preselection of several stored timings, which can be called back from memory by a single button press.
Mechanical
Early photolab timers used a clockwork mechanism to measure time.
“Photo-lab timer” enters the record as timer for enlarging in dark room. Crown Archives preserves that source wording while asking what Photo-lab, timer and Timer can confirm, complicate or overturn.
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This entry incorporates text from “Photo-lab timer” on English Wikipedia. Contributors are listed in the page history. Text is available under the Creative Commons Attribution-ShareAlike 4.0 License. Selected authority identifiers and statements are retrieved from Wikidata under CC0; their references and qualifiers remain part of the verification path.