Shutter Angle Calculator
Shutter angle to shutter speed and back, with the 180 degree rule, the flicker safe angles for 50 and 60 hertz mains, and a slow motion conform module that tells you what the take becomes on the timeline.
Calculator
Shutter angle against shutter speed, in one paragraph
They describe the same thing and they are not interchangeable. Shutter speed is an absolute length of time: 1/48 of a second is 1/48 of a second on any camera at any frame rate. Shutter angle is a proportion: it says what fraction of each frame the sensor was exposed for, so 180 degrees always means half the frame, whatever the frame rate is.
That difference decides which one you should be speaking. Say 180 degrees to a camera operator and the look is fixed no matter what frame rate they are on. Say 1/48 and the look changes the instant the frame rate does, because 1/48 at 24 fps is a 180 degree shutter and 1/48 at 48 fps is a 360 degree shutter, which is a completely different image. Angle travels. Speed does not.
Photographers grew up with speed because a still frame has no frame rate to divide by. Cinema grew up with angle because a physical disc really was cut at an angle. Both are correct in their own world, and the calculator above converts between them in either direction.
Who this is for
- Anybody whose camera shows one unit and whose director speaks the other. Convert once, write it in the camera notes, and stop translating in your head on set.
- Anybody shooting under mains lighting. Use the flicker safe angles this page prints for your frame rate before you discover the banding in the edit.
- Anybody shooting slow motion. The conform module below tells you what the take becomes on the timeline and, more usefully, how long to roll for.
- Anybody learning. The formula is closed, public and short. Read the next section once and you will never need this page again, which is the highest compliment a calculator can pay itself.
The formula is closed and public
There is no mystery and no proprietary table here. A film camera has a rotating disc with a wedge cut out of it. The size of that wedge, in degrees, decides what fraction of each frame the sensor or the film is exposed for.
Digital cameras have no disc, but the industry kept the vocabulary because it travels better than shutter speed does. An angle is independent of frame rate. If you tell a camera operator 180 degrees, the look is the same whether they are shooting 24, 25 or 48 frames a second. If you tell them 1/48, the look changes the moment the frame rate does.
The 180 degree rule
A 180 degree shutter exposes each frame for exactly half its duration. That ratio is what most of cinema was shot on, so the amount of motion blur it produces is what an audience reads as normal. Narrower angles freeze motion and make movement look sharp and slightly nervous, which is why the beach landing in a war film is not shot at 180. Wider angles smear, which is used deliberately for dream states and drunkenness, and accidentally by people who left the camera on auto.
It is a convention, not a law. What matters is knowing which one you are choosing and why.
Why 172.8 degrees exists
This is the number that confuses people, and it is pure electrical engineering. Under mains lighting at 50 hertz, lamps pulse 100 times a second. To avoid banding you want your exposure to be a whole multiple of 1/100 of a second. At 24 fps, a 180 degree shutter gives 1/48, which is not a multiple of 1/100, so the pulse and the exposure beat against each other and you get flicker.
Solve for the angle that gives exactly 1/50 at 24 fps and you get 172.8 degrees. It is visually indistinguishable from 180 and it kills the flicker. Under 60 hertz mains, the same logic points at 1/60 or 1/120 instead. The calculator above prints both flicker safe angles for whatever frame rate you type, so you do not have to work it out on set.
How indistinguishable? Going from 180 to 172.8 degrees is a change of 0.059 of a stop, which is about a sixteenth of a stop. Nobody has ever seen it. The flicker, on the other hand, is unmissable and cannot be graded out.
The flicker safe angles, worked out
Every value here is the same formula, angle equals 360 times the frame rate divided by the exposure denominator, solved for the exposures that are whole multiples of the mains pulse.
| Frame rate | 50 Hz, 1/50 | 50 Hz, 1/100 | 60 Hz, 1/60 | 60 Hz, 1/120 |
|---|---|---|---|---|
| 23.976 fps | 172.6 | 86.3 | 143.9 | 71.9 |
| 24 fps | 172.8 | 86.4 | 144 | 72 |
| 25 fps | 180 | 90 | 150 | 75 |
| 29.97 fps | 215.8 | 107.9 | 179.8 | 89.9 |
| 30 fps | 216 | 108 | 180 | 90 |
| 50 fps | 360 | 180 | 300 | 150 |
| 59.94 fps | over 360 | 215.8 | 359.6 | 179.8 |
| 60 fps | over 360 | 216 | 360 | 180 |
| 100 fps | over 360 | 360 | over 360 | 300 |
| 120 fps | over 360 | over 360 | over 360 | 360 |
Two things fall out of that table that are worth carrying around. Twenty five frames a second on 50 hertz mains is flicker safe at exactly 180 degrees, and thirty frames on 60 hertz mains is flicker safe at exactly 180 degrees too. That is not luck. The broadcast standards were built around the mains frequency of the countries that made them, which is also why 25 and 30 exist as separate numbers at all.
The other is a hard limit. Above 100 frames a second on 50 hertz mains there is no flicker safe shutter at any angle, because even a fully open 360 degree shutter exposes for less than 1/100 of a second. If you have to shoot high speed under cheap mains lighting, the shutter cannot save you. The answer is different lighting, not a different angle.
What the angle costs you in light
Shutter angle is an exposure control as much as a look control, and the arithmetic is the same as any other stop. Halve the angle and you halve the light, which is one stop.
- 180 degrees to 90 degrees is one stop darker. 90 to 45 is another.
- 180 degrees to 270 degrees is just over half a stop brighter, 0.58 of a stop, and 180 to 360 is a full stop brighter.
- 180 to 172.8, the flicker fix, is 0.059 of a stop. Ignore it.
The change that catches people is the frame rate, because holding the angle while raising the frame rate costs light silently. Keep 180 degrees and go from 24 fps to 48 and you lose exactly one stop. To 60 fps you lose 1.32 stops. To 120 fps, 2.32 stops. To 240 fps, 3.32 stops.
This is the single most common mistake in high speed work. Somebody lights a beautiful shot at 24 fps, switches to 120 for the slow motion take, and the image goes dark by more than two stops without a single setting having visibly changed. The fix is more light or a wider iris, decided before the take rather than discovered during it.
Slow motion and conform
Slow motion, overcranking and conform
Shooting at a higher frame rate than the timeline is called overcranking, from the days when the camera really was cranked by hand. Play 120 frames a second back on a 24 frame timeline and each second of reality takes five seconds of screen time, so the action runs at twenty percent speed.
The trap is the shutter. Your shutter angle is set against the capture rate, not the timeline. At 120 fps, a 180 degree shutter is 1/240 of a second, which is a short exposure and needs a lot more light. This catches people out constantly: they set up a beautiful shot at 24 fps, switch to 120 for a slow motion take, and lose 2.32 stops without touching the aperture.
The second trap is the conform. If a director asks for a slow motion insert that runs four seconds on screen, and you are shooting 120 fps for a 24 fps timeline, you need to roll for four fifths of a second of real action. In practice you roll longer, but the point stands: the take is short and the moment has to happen inside it.
The whole table, if you prefer to read it
| Frame rate | 45 deg | 90 deg | 172.8 deg | 180 deg | 270 deg | 360 deg |
|---|---|---|---|---|---|---|
| 23.976 fps | 1/192 | 1/96 | 1/50 | 1/48 | 1/32 | 1/24 |
| 24 fps | 1/192 | 1/96 | 1/50 | 1/48 | 1/32 | 1/24 |
| 25 fps | 1/200 | 1/100 | 1/52 | 1/50 | 1/33 | 1/25 |
| 29.97 fps | 1/240 | 1/120 | 1/62 | 1/60 | 1/40 | 1/30 |
| 30 fps | 1/240 | 1/120 | 1/62 | 1/60 | 1/40 | 1/30 |
| 48 fps | 1/384 | 1/192 | 1/100 | 1/96 | 1/64 | 1/48 |
| 50 fps | 1/400 | 1/200 | 1/104 | 1/100 | 1/67 | 1/50 |
| 59.94 fps | 1/480 | 1/240 | 1/125 | 1/120 | 1/80 | 1/60 |
| 60 fps | 1/480 | 1/240 | 1/125 | 1/120 | 1/80 | 1/60 |
| 96 fps | 1/768 | 1/384 | 1/200 | 1/192 | 1/128 | 1/96 |
| 100 fps | 1/800 | 1/400 | 1/208 | 1/200 | 1/133 | 1/100 |
| 120 fps | 1/960 | 1/480 | 1/250 | 1/240 | 1/160 | 1/120 |
| 240 fps | 1/1920 | 1/960 | 1/500 | 1/480 | 1/320 | 1/240 |
Rounding, and what cameras actually let you set
Very few cameras offer a continuous shutter. Most give you steps, and the steps are not always the value you asked for. If the calculator says 1/47.952 and the camera offers 1/48, take 1/48. The difference is a thousandth of a stop and no audience has ever seen it. What matters is not being a whole stop out, or landing on a shutter that beats against the lights.
One more piece of set discipline. Many cameras let you display either angle or speed and remember the last one you used. When two cameras on the same job are set differently, one in angle and one in speed, and someone changes a frame rate on only one of them, the two units drift apart and the mismatch shows up in the grade. Pick angle for the whole job and put it in the camera notes.
Where this calculator stops being the answer
The conversion is exact. These are the situations where an exact conversion is not what you need.
The blur is already in the file. Motion blur is created at the moment of exposure and is then part of the picture. No editing or grading application can remove it, and the ones that add it are synthesising new blur on top rather than recovering the shutter you did not use. If the take was shot at 45 degrees and the director wanted 180, the take was shot at 45 degrees.
The camera does not offer the value. Very few cameras give a continuous shutter. Most offer steps, and the step nearest your answer is almost always fine. What is not fine is being a whole stop out, or landing on a shutter that beats against the lights.
Rolling shutter is a separate problem. Skew on fast pans, and the wobble people call jello, come from the sensor reading out line by line rather than all at once. Narrowing the shutter angle freezes each line more crisply and does nothing about the skew, because the readout time is not the exposure time. Changing the angle will not fix it. Slowing the pan will.
Exposure has three controls and this is only one of them. Reaching for the shutter to fix exposure is what quietly destroys a look, because the shutter is the one control that changes how motion reads. On a bright exterior the right answer is almost always neutral density in front of the lens, which lets you hold both the angle and the iris you chose. Use the shutter for the look and let the filters carry the light.
The word shutter inside editing software. Editing and grading applications expose a shutter angle field of their own. It controls synthetic motion blur applied to motion the software is generating, such as a speed ramp or an animated graphic. It is the same idea borrowed for a different job, and it has no effect on the blur that came out of the camera.
Common questions
What shutter speed is a 180 degree shutter?
Angle divided by 360 times the frame rate. At 24 fps a 180 degree shutter is 1/48 of a second, at 25 fps it is 1/50, at 30 fps it is 1/60 and at 60 fps it is 1/120.
Why do some cameras use 172.8 degrees?
Under 50 hertz mains the lights pulse 100 times a second, so the exposure needs to be a multiple of 1/100 to avoid banding. At 24 fps, 172.8 degrees gives exactly 1/50 of a second, which is flicker safe and looks the same as 180.
What shutter angle should I use for slow motion?
The angle is set against the capture frame rate, so 180 degrees at 120 fps means 1/240 of a second. Keeping 180 degrees keeps the motion blur consistent, but it costs light, which is why high speed work needs more of it.
Is shutter angle the same as shutter speed?
They describe the same exposure, in different units. Speed is an absolute time. Angle is the fraction of each frame the sensor was open for. At 24 fps, 180 degrees and 1/48 of a second are identical. At 48 fps, 180 degrees is 1/96 and 1/48 has become a fully open 360 degree shutter. Same numbers, completely different image, which is why the frame rate always has to be part of the sentence.
Should I set my camera in shutter angle or shutter speed?
Angle, if the camera offers it, and especially on any job that changes frame rate. An angle survives a frame rate change and keeps the look consistent, and it is the language a camera department already speaks. Speed is the better unit only when you are matching something absolute, such as a practical light or a screen that flickers at a known frequency, because then the time itself is what you are locking to.
What shutter angle should I use for 60fps?
180 degrees, which is 1/120 of a second, if you want normal looking motion. That is the default answer and it holds at every frame rate, which is the entire point of thinking in angles. Under 60 hertz mains, 180 degrees at 60 fps is already flicker safe. Under 50 hertz mains you want 216 degrees instead, which gives exactly 1/100 of a second.
What shutter angle should I use for 120fps?
180 degrees again, which is 1/240 of a second, and this is where you have to plan the light rather than discover it. Holding 180 degrees from 24 fps to 120 fps costs 2.32 stops. Under 60 hertz mains, 360 degrees at 120 fps gives exactly 1/120 of a second and is flicker safe, but it is also a fully open shutter, so the motion blur will not match anything else you shot. Under 50 hertz mains there is no flicker safe option at 120 fps at all.
Does shutter angle affect exposure?
Yes, directly, and it is ordinary stop arithmetic. Halving the angle halves the light. Going from 180 to 90 degrees is one stop darker, 90 to 45 is another. Going from 180 to 360 is a stop brighter. This is why the shutter is a dangerous place to fix an exposure problem: it works, and it changes the way motion looks while it works.
Does shutter angle affect motion blur?
It is the only thing that does. A wider angle keeps the shutter open for a larger fraction of each frame, so a moving subject travels further while the sensor is collecting light, and the smear is longer. A narrower angle freezes it. At 180 degrees the smear covers half the distance the subject travelled in that frame, and that ratio is what a century of cinema trained audiences to read as normal.
Can you change shutter angle in post?
No. The blur is baked in at the moment of exposure and there is nothing to recover. You can add more blur, with frame blending or a motion blur effect, and that sometimes rescues a shot that was accidentally shot too narrow. You cannot subtract blur that is already there. This is why the shutter is a decision to make on the day, and why it belongs in the camera notes rather than in your memory.
Why is it called the 180 degree rule?
Because a film camera really did have a rotating disc with a wedge cut out of it, and a wedge cut at 180 degrees is exactly half the disc. Half the disc open means the film is exposed for half of each frame and covered for the other half, while the mechanism pulls the next frame into place. That mechanical fact became the look of cinema, and the name stayed on long after the disc disappeared. One warning about the name. There is a second, completely unrelated 180 degree rule, about camera placement and the line of action between two actors. Same number, different subject, and confusing them in a conversation with a director is an unforced error.