Exposure timer
An exposure timer is a short-term timer used in the photo laboratory . It is used to precisely control the lamp in the enlarger . It is often (imprecisely) referred to as a laboratory clock.
function
After a period of time has been specified, the power supply to the enlarger is activated for the desired duration at the push of a button, thus performing an exact and reproducible exposure process. The selectable time range is typically between 1/10 of a second up to one or more minutes. Most exposure timers also have a switch for permanent light, which is particularly helpful for setting up the image section and focusing .
Designs
Depending on the version, the desired duty cycle is set using a mechanical dial with a scale or a push button arrangement along with a numeric display. More comfortable variants allow the preselection of several times, which can be called up specifically at the push of a button.
alternative
Magnifiers with a light quantity meter measure the amount of light per area regardless of the magnification and the mains voltage and therefore allow more precise exposure.