ShutterMeter measures the real duration of each shutter speed on a mechanical film camera, using the iPhone's microphone to time the opening and closing transients. Results are graded honestly: when the signal isn't clean, the app says "Reference" instead of pretending.
Support / 支持： questions and bug reports to szpwqq@gmail.com. Include your camera model and the shutter speed you were testing, and I'll get back to you.
Microphone mode covers 1s–1/60, including the vintage scale speeds (1/5, 1/10, 1/25, 1/50). Each camera gets its own log, so you can watch a shutter drift over the years and get concrete exposure compensation advice. Speeds of 1/500 and faster are physically out of reach for a phone, and the app says so instead of guessing.
Everything is analyzed on your iPhone; nothing is uploaded. Details in the privacy policy.