Shutter angle and 180° rule.

Worked example

At 24 fps with a 180° shutter, exposure time = (180 ÷ 360) ÷ 24 = 1/48 s. Most cameras offer 1/50, which is a 172.8° angle. At 30 fps the 180° speed is 1/60; at 60 fps it is 1/120.

How it works

The shutter angle is the fraction of each frame interval the shutter is open, in degrees: angle ÷ 360 = exposure time ÷ frame interval. So exposure time = (angle ÷ 360) ÷ fps and angle = 360 × fps × exposure time. The 180-degree rule sets the shutter to half the frame interval, which is the shutter angle described as normal for cinema and gives a natural amount of motion blur.

A smaller angle (faster shutter) gives crisper, choppier motion; a larger one gives more blur. Artificial lights can flicker on screen at some shutter speeds; test under your lighting. Most cameras offer a limited speed list, so the tool also shows the nearest standard setting.

Sources and basis (checked 2026-10-05): Wikipedia: Rotary disc shutter (shutter angle / 360° = exposure time / frame interval; 180° considered normal; 1/50 s at 24 fps is about 173°). Arithmetic on the numbers you enter.

FAQ

What is the 180-degree shutter rule?

Set the shutter speed to about double the frame rate, which means the shutter is open for half of each frame interval. At 24 fps that is 1/48 s.

What shutter speed for 24fps?

1/48 s for a true 180° shutter. Cameras without 1/48 usually offer 1/50, which is 172.8°.

What shutter speed for 30fps and 60fps?

1/60 s at 30 fps and 1/120 s at 60 fps for a 180° shutter.

What is a shutter angle?

The fraction of a full 360° rotation the shutter is open per frame, a film-camera idea now used on many cinema cameras instead of shutter speed.

Should I always shoot at 180°?

It is the normal default, not a law. Use a smaller angle for sharper action or a larger one for dreamy blur or low light.