How the Cine Shutter Angle works

Summary

Calculator that converts cine shutter angle (degrees) and frame rate (fps) to a still-camera shutter speed so the meter can speak the same language.

How it works

Cine cameras describe shutter speed as an angle, not as a fraction of a second. The shutter is a rotating disc with a wedge cut out of it. The size of that wedge in degrees, plus the frame rate, decides how long each frame is exposed. This modal converts angle and frame rate into a still-camera shutter speed so the meter can speak its language.

Shutter angle

Measured in degrees from 1 to 360. A 180-degree shutter is the cinematic default and gives the natural-looking motion blur audiences are used to. A 360-degree shutter gives the most light and the most motion blur. A small angle like 45 degrees gives crisp, almost stop-action motion.

Frame rate

Frames per second. 24 fps is film standard. 25 is PAL. 30 or 29.97 is NTSC. 48 to 60 is high frame rate. The faster you shoot, the shorter each frame's exposure becomes at the same shutter angle.

The math

Shutter speed in seconds equals shutter angle divided by 360, divided by frame rate. A 180-degree shutter at 24 fps is 1/48 of a second. A 90-degree shutter at 60 fps is 1/240.

Why the 180-degree rule matters

Doubling the frame rate while keeping motion blur natural means halving the shutter angle, or doubling the shutter speed. If you shoot 48 fps for slow motion, set a 180-degree shutter angle (which gives 1/96), not the 1/48 you used at 24 fps.