How to use this shutter angle calculator
- Choose the value to solve: shutter speed, shutter angle, or recording frame rate. Enter the other two.
- Use exact fractional-rate presets for 23.976, 29.97, and 59.94 workflows. Recording rate determines exposure; playback rate does not.
- Select a lighting assumption or enter a measured light pulse frequency. Read the cycle comparison and try a candidate if your camera supports it.
- Copy or print the card. Record test footage with the real lights and dimmer levels, and inspect the recorded clip for brightness changes and bands.
Shutter angle to shutter speed
Shutter angle describes the exposed fraction of one frame interval. A 180° angle exposes for half the interval: at 24 fps that is 1/48 second, at 25 fps 1/50, and at 60 fps 1/120. A smaller angle shortens exposure and a larger angle lengthens it.
The blur comparison is exposure-time-based, relative to 180° at the same frame rate. Actual visible blur also depends on subject and camera motion. The calculator limits angle to 360°; multi-frame slow-shutter accumulation is not modeled. Individual cameras may impose tighter angle, speed, or readout limits.
Why fractional frame rates matter
The common 29.97 preset uses 30000/1001 fps, not exactly 30 fps. At 180° it produces approximately 1/59.94006 second. For an exact 1/60-second exposure at that recording rate, the angle is approximately 179.82018°.
Likewise, 172.8° gives exactly 1/50 second at 24 fps, but not at 24000/1001 fps. The candidate table derives the angle from the entered recording rate rather than treating rounded labels as integers.
Exposure formulas
Exposure time (s) = angle ÷ (360 × recording fps)Angle (°) = exposure time (s) × recording fps × 360Recording fps = angle ÷ (360 × exposure time (s))Whole-cycle candidate time (s) = positive integer cycles ÷ light pulse HzTiming error (%) = |entered time − candidate time| ÷ candidate time × 100Only whole-cycle durations that fit within one frame are listed. The table shows up to eight candidates closest to the current exposure; it is not a list of every camera-supported shutter increment.
50 Hz and 60 Hz lighting
For the selected mains models we assume two light pulses per power cycle: 100 pulses/s for 50 Hz, or 120 pulses/s for 60 Hz. Under this ideal periodic model, integrating a positive integer number of light cycles removes dependence on the exposure's starting phase. This is the mathematical basis for our candidates, not a measurement of your light.
At 24 fps, 1/50 second corresponds to 172.8° and two cycles at 100 Hz; 1/60 corresponds to 144° and two cycles at 120 Hz. At 120 fps under the 100 Hz model, no full light cycle fits within one frame.
LED, PWM, and rolling-shutter limitations
Some LED fixtures and displays repeat independently of mains frequency. Dimming may change their pulse pattern. Mixed sources may have different frequencies, and a nominal frequency can drift. Camera readout timing can also affect how bands appear.
Our comparison does not simulate a waveform, rolling-shutter scan, duty cycle, synchronization, or frame-to-light phase locking. Near-cycle tolerance describes timing arithmetic only. Use your camera's fine shutter adjustment where available, and judge the recorded footage rather than relying solely on a monitor preview.
Frequently asked questions
Is the 180-degree shutter rule mandatory?
No. It is a common starting point for exposure-time motion blur. A different angle may suit your shot or lighting. Changing exposure time also changes the light integrated per frame; adjust other exposure settings as needed.
Is 1/125 the same as 1/120 under 60 Hz lighting?
No. 1/125 is 8 ms and spans 0.96 cycles at 120 Hz; 1/120 spans exactly one modeled cycle. Some camera increments or real lighting can still yield usable footage at 1/125, but the calculator does not equate the two.
Why does the table show no candidates?
One complete modeled light cycle may be longer than a frame interval. A full cycle then requires an angle above 360°. Change the lighting or recording rate, or test another camera strategy. This does not prove every shorter exposure will visibly flicker.
Can I enter a shutter speed as just 50?
Use 1/50 for one-fiftieth of a second. A bare 50 means 50 seconds. You can also enter 20 ms or 0.02 s. Impossible single-frame exposures are rejected rather than silently adjusted.
Are these settings guaranteed on my camera?
No. This is a timing calculator, not a camera compatibility database. Check supported angles, shutter speeds, frame rates, and readout constraints in your camera's manual.
Camera references
RED's shutter documentation explains angle/speed conversion. Its flicker tutorial discusses light-pulse timing and real-source complications. Sony's flicker guidance covers fine shutter adjustment and checking recorded footage.