Shutter-Speed works together with the PhotoPlug - a small sensor which connects to the headphone jack of your smartphone. If your smartphone has no headphone jack, you can use a TRRS adapter cable.
The sensor is available at www.filmomat.eu. There you also find further information about this App.

Together with the PhotoPlug, this App transforms your smartphone into an optical shutter speed tester for analog cameras. Just open the back of the camera, point the lens towards a bright light source and position the PhotoPlug behind the camera. Once you release the shutter, the App will display a waveform with two peaks: One peak when the shutter opens, another one when the shutter closes. The time between those peaks reassembles the shutter speed of your camera. The App also calculates a deviation value in f-stops and allows you to save measurements to your phone.

Acoustic mode: The App will also work without the optional PhotoPlug sensor. Without the sensor, the App records the sound of the camera shutter (shutter release sound). This works, because the shutter makes a noise when it opens and closes. Please note that this is only suitable for shutter speeds slower than 1/30sec. Faster speed will not give useable results.