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About this tool
Convert between shutter angle and shutter speed at any frame rate, with a flicker check for 50 Hz and 60 Hz mains.
The Shutter Angle Calculator converts between the rotary shutter angle a cinema camera displays and the 1/x shutter speed a stills-derived menu asks for, at any frame rate. The relationship is exposure time = angle / (360 x fps), so the familiar 180-degree rule — exposing for half of each frame interval — gives 1/48 s at 24 fps and 1/50 s at 25 fps. It also checks the resulting exposure against 50 Hz and 60 Hz mains lighting, which pulses at twice the supply frequency and causes rolling bands when the exposure does not span a whole number of pulses.
Open Shutter Angle Calculator on AltFTool — it loads instantly in your browser.
Enter the values you already know.
Fine-tune the options to match your scenario.
Read the result and use it in your planning or reporting.
Enter an angle to get the speed, or a speed to get the angle your camera would call it.
Flags exposures that will band under mains lighting and offers the nearest safe angle.
Reports how many stops each angle sits from the 180-degree reference so you can compensate.
It is half the frame interval, so the denominator is twice the frame rate: 1/48 s at 24 fps, 1/50 s at 25 fps, 1/60 s at 30 fps and 1/120 s at 60 fps. The formula is shutter speed denominator = 360 / angle x fps.
Because 360 / 172.8 x 24 = exactly 50, so a 172.8-degree shutter at 24 fps gives a 1/50 s exposure, which is flicker-free under 50 Hz mains lighting. It is only 0.06 of a stop darker than 180 degrees, so the motion blur is visually identical.
Choose an exposure time that spans a whole number of light pulses. Mains-powered discharge and non-DC LED lamps pulse at twice the supply frequency, so use 1/50 or 1/100 s on a 50 Hz supply and 1/60 or 1/120 s on 60 Hz. Dimmed or PWM-driven LEDs flicker at their own rate, so always confirm on a monitor.
Yes — halving the angle halves the light, which is one stop. Going from 180 to 90 degrees costs a stop, and 180 to 45 degrees costs two, so you need to open the iris, raise ISO or add light to keep the same brightness while getting crisper motion.
Add the Shutter Angle Calculatorwidget to your blog or website — free, responsive, no signup. Just keep the “Widget by AltFTool” credit link visible.
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