This mechanism automatically changes the diameter of an optical stop after a preset duration. It is used in specialized exposure systems and time-resolved imaging to control the amount of light reaching a sensor or film without manual intervention. By regulating the light flux over time, it ensures precise exposure profiles for complex imaging tasks.
Heard on the job
Set the time stop to close down one stop after three seconds to avoid blowing out the background during the long exposure.
Insider tip
While electronic shutter controls handle this in digital sensors, mechanical time stops remain relevant in specialized optical testing and legacy film equipment.