The device consists of three BPW34 photodiodes, a mechanical switch, a resistor, microphone wire, and a 3D-printed case. The photodiodes are arranged in a line with an offset to one edge of the frame window to compare shutter movement uniformity and detect jams or delays.
The sensors are connected in parallel, with the outer ones passing through a switch. For data collection, Audacity software with maximum gain was used. The light source is a bright flashlight positioned perpendicularly to the lens mount at a distance of 25–35 cm.
A load resistor of 470–1000 Ohms converts the photocurrent into a signal compatible with a PC's input dynamic range. This low shunt resistance reduces the circuit's time constant, eliminating signal drops during fast shutter movements and preserving pulse detail.
The tester operates for shutter speeds of 1/250 second and faster using three sensors, while a single central sensor is used for speeds of 1/125 second and longer. The method determines exposure time by measuring the distance between the signal's rise and fall on the graph.
Testing a Zenit-ET camera showed that the shutter initially operated at less than 22 ms for a 1/30 s setting. After adjustment, it reached 28 ms, which falls within the GOST 19821–83 tolerance of +36% to −28%. For 1/250 s, the central sensor recorded exactly 4 ms.