0 a device, usually held away from a camera, that automatically makes a flash when a camera is taking a picture
Using a flashgun to illuminate a line of white disks, they were able to generate intense afterimages in dark-adapted observers.
The 100/104 designation refers to the type of flash: models ending in 0 had a built-in flashgun, while those ending in 4 used flashcubes.
Observers were required to verbally report how many disks had been presented, both at 10 s and at 60 s after the flashgun exposure.
About a year later, a threaded hole was added at the right-hand front above the flashbulb synchronising contacts for securing the flashgun to the camera (version 4).
An external electronic flashgun was also available.
