Flicker-Free Shutter Calculator

Knowledge Base

Why Shutter Speed Causes Flicker

Mains-powered lights that aren't on a flicker-free driver actually pulse at twice the mains frequency. A 60Hz supply produces 120 pulses per second, a 50Hz supply produces 100. If your shutter is open for a duration that isn't a whole multiple of that pulse period, you capture a different amount of light in each frame, which shows up as visible banding or flicker, especially in slow motion or when panning past fluorescent tubes.

The Rule of Thumb

Match your region's mains frequency to your shutter speed family: on 60Hz power, shutter speeds like 1/60, 1/120, and 1/240 are safe. On 50Hz power, use 1/50, 1/100, or 1/200. This is why many cameras default to a 180-degree shutter at a frame rate matching local power. It lines up automatically.

What About LED Lights?

Cheap LED panels and practicals often flicker at mains frequency just like old fluorescent tubes, so the same safe shutter speeds apply. Higher-end LED fixtures with flicker-free or high-frequency drivers (and continuous sources like daylight, tungsten, or HMI on a flicker-free ballast) don't pulse at all, so any shutter speed is safe from a flicker standpoint, though the 180-degree rule still applies for natural motion blur.

FAQ

Q: I'm shooting slow motion at a high frame rate, does the rule change?
A: No, the safe shutter speeds are still whole multiples of the mains pulse period, but at high frame rates you may need a much faster shutter than a 180-degree angle would give you, which can mean stepping outside 180 degrees or accepting some risk of flicker.

Q: My mains frequency is right but I still see flicker, why?
A: Some ballasts and drivers (particularly older or faulty ones) don't produce a clean, symmetric pulse: try the next safe shutter speed up or down, or test in-camera before the real shoot.