Is it possible to calculate the shutter speed of a camera when you shoot single frame?

[Ruben Arce]

I've been breaking my head and I can't find a solution to this question. I know the shutter angle of a movie camera determines to an extent the exposure of the single frame. Since we don't know the speed at which the shutter rotates (single frame) it is impossible to make a rule about this imo. I guess the only way to know the shutter speed of a camera is checking the manual and seeing what the manufacturer says.

The manual of the Scoopic M says in order to calculate exposure using the camera you must set the camera at the 16fps position, take a reading and go back to single frame. I can use that information to use my handheld light meter, but I'm trying different cameras and I would like to be able to calculate the shutter speed using the shutter angle if that's possible.

[Simon Wyss]

You have understood that the quantity of light the film receives is compound of the luminous flux and time. While the opening angle of a rotary disc shutter determines exposure time at a given speed of the mechanism it will be the actual construction of the camera and the state it’s in lubrication-wise that make for how fast everything moves.

An electric motor also takes time to accelerate. With some cameras the start is very fast, with others slower. You simply cannot calculate nor know unless you bracket exposure or measure revolving rates of your camera with the aid of special equipment.

I should advise to take an exposure time prolonged by the factor 1.5 for a beginning, so 1/23th of a second instead of 1/34th for 170 degrees shutter angle.

[Ruben Arce]

Thanks Simon.

[Dom Jaeger]

There are a few cheap options for measuring the shutter speed of film cameras, including DIY Arduino builds or smartphone apps (these need a phone that has a headphone jack for the photoplug accessory), but the simplest way is to shoot slo-mo on an iPhone at 240fps, pointing at the lens with a light shining through the gate. You can then analyse the footage and count how many frames the light is visible, 6 frames means the shutter speed is around 1/40 sec, 7 frames and it's around 1/35 sec etc. Or any still camera repair shop should have a shutter speed tester. 

[Robino Jones]

You can get this little device:
https://www.catlabs.info/product/photoplug-optical-shutter-speed-tester

I got one to figure out single frame exposure times for a very custom camera that has no manual ? I setup a small flashlight on a c-stand pointing at the lens mount, and then used the app to calculate the shutter speeds. It worked well and the film came back nicely exposed.