Cine Shutter Angle Calculator
Cinema cameras describe exposure by shutter angle, a holdover from the spinning disc shutters of film cameras: the open arc of the disc sets how long each frame is exposed. This calculator converts a shutter angle and frame rate into the equivalent shutter speed in seconds and as a 1-over fraction, and back the other way. It also reports the shutter speed for the classic 180-degree rule at your frame rate. Use it to match motion blur across cameras and to dial in the look you want.
Shutter angle formula
Exposure time t = angle / (360 * fps) (seconds)
One-over value = 1 / t
180-degree rule: t = 1 / (2 * fps)
To reverse: angle = t * 360 * fps
The exposure is the fraction of the frame interval that the shutter is open. A 180-degree shutter is open for half of each frame.
Cine shutter context
- 180 degrees is the standard, giving natural film-like motion blur.
- Smaller angles freeze motion with a crisp, staccato look.
- Larger angles add motion blur and a softer, dreamier feel.
- Changing the angle changes brightness, so compensate with aperture or ISO.
- Matching shutter angle across cameras keeps motion blur consistent.
Shutter angle: frequently asked questions
How does shutter angle relate to shutter speed?
Shutter angle comes from rotary film shutters: the open arc of a spinning disc. Exposure time equals the angle divided by 360, divided by the frame rate: t = angle / (360 times fps). At 24 fps a 180 degree shutter exposes for 1/48 second, the classic film look.
What is the 180-degree shutter rule?
The 180-degree rule says set the shutter angle to 180 degrees, which makes the exposure half of the frame interval. At 24 fps that is 1/48 second, at 30 fps it is 1/60 second. It gives natural-looking motion blur that audiences are used to in film and television.
How do I convert shutter speed back to an angle?
Rearrange the formula: angle = shutter speed times 360 times the frame rate. A 1/50 second exposure at 25 fps gives an angle of (1/50) times 360 times 25, which is 180 degrees. This calculator does both directions.
What happens with a smaller or larger shutter angle?
A smaller angle (like 45 or 90 degrees) shortens the exposure, freezing motion and giving a crisp, staccato look, as in some action scenes. A larger angle (toward 360 degrees) lengthens the exposure, adding more motion blur and a dreamier feel. The trade-off is sharpness versus blur.
Does shutter angle change exposure brightness?
Yes. A wider angle exposes each frame for longer, letting in more light, while a narrower angle lets in less. Changing the angle changes brightness just like changing shutter speed, so you compensate with aperture, ISO, or lighting to keep exposure constant.
Official sources
- SMPTE: motion-imaging frame rate and shutter standards.
- CIPA: Camera and Imaging Products Association standards.
Reviewed by the CalculatorHub team, edited by James Graham, 17 June 2026. See our methodology.