User:Mcapdevila/Photo-lab timer

Electronic Timer-Analyzer

A photo lab timer, photo interval timer, or darkroom timer is a device used in photography for timing the processes of enlarging negatives on paper or for making them at any scale. It is a device to which the photo lab enlarger is attached to ensure that the duration of photo exposures on sensitive paper can be carried out accurately.

Initially they were conventional clocks and later they were replaced by entirely electronic equipment. When the selected time has elapsed, the enlarger is simply turned off or an alarm is sounded, for the photographer to turn it off

mechanic

Durst Digitimer

Clock for mechanical use to measure time. Manual timers are usually set by turning a dial to the desired time interval, turning the dial stores energy in a mainspring to operate the mechanism. They work similar to a mechanical alarm clock, the energy of the mainspring causes a balance wheel to turn back and forth. Each turn of the wheel frees the gear train to advance a small, fixed amount, causing the dial to move steadily back until it reaches zero and then a lever arm strikes a bell. The mechanical enlarger timer was invented in the 1920s with a stabilizer that rotates against air resistance .

Gra-Lab electromechanical timer.

Electromechanical

Short period electromechanical timers for enlargers use a mechanism driven by an AC synchronous motor without any electronic circuitry. When the selected time has elapsed, the amplifier is disconnecThe electric current feeds the synchronous motor which is supported by gear reducers that rotates the seconds hand one turn every minute and simultaneously, the minute hand one turn every hour, thus achieving timings of up to 60 minutes with an accuracy of a second. ted via the relay that kept it on.

The electric current feeds the synchronous motor which is supported by gear reducers that rotates the seconds hand one turn every minute and simultaneously, the minute hand one turn every hour, thus achieving timings of up to 60 minutes with an accuracy of a second.

electronic

magnifier timer.

Electronic timers are essentially quartz clocks with special electronics and can achieve higher accuracy than mechanical or electromechanical timers. Electronic timers have digital electronics, but can have an analog or digital display .

Integrated circuits have made digital logic so cheap that an electronic timer is now less expensive than many mechanical and electromechanical timers. Individual timers are implemented as a simple single-chip computer system, similar to a clock and usually using the same, mass-produced technology.

Automatic timer/analyzer

Electronic analyzer

There is an automatic timer from Kaiser, Philips, and others that regulates the exposure time according to the light projected by the enlarger, on the sensitive paper, through the negative. Automatic enlarger timer "Switch and exposure meter for B/W and color negatives and slides. Selective or integral exposure measurement using an independent metering head with a silicon optical sensor and converging lens. Three digits, display amber digital . start button preparation screen . time step in the time cycle with countdown to zero . button to stop and resume the countdown of the remaining running time as well as refraction measurement with direct time reset It can also be used as a manual exposure timer with setting the desired time using the up/down buttons.

External links

• «Darkroom Process control / Timers». fotoimpex.com analogue photography. [Consulta: 21 abril 2023].

[[Category:Clocks]] [[Category:Photography]]