High Speed and Slow Motion Video

High Speed and Slow Motion Video

Slow motion video is created by shooting at a higher frame rate than the playback frame rate. When you shoot at 120 fps and play back at 30 fps, the action is four times slower. This reveals details that are invisible at normal speed, like the exact moment a droplet of water splashes or the subtle wing movement of a hummingbird. High speed video opens up a world of motion that our eyes cannot normally perceive.

Shutter speed becomes more critical in slow motion. The 180-degree rule still applies. For 120 fps slow motion, use a shutter speed of 1/240 second. This gives you natural motion blur between frames. If you use a faster shutter speed, each frame will be too sharp and the slow motion will look staccato and unnatural. If you use a slower shutter speed, you get excessive blur between frames.

Lighting is the biggest challenge for high speed video. Shooting at 120 fps with a shutter speed of 1/240 second requires a lot of light. At 240 fps with a 1/480 shutter speed, you need even more. This is why high speed shots often look darker than normal footage. You may need to open the aperture to its widest setting, raise ISO higher than usual, or add supplemental lighting to get a properly exposed slow motion shot.

Rolling shutter artifacts become more noticeable in slow motion. Most cameras use a rolling shutter that reads the sensor line by line rather than all at once. At high frame rates, the sensor readout is faster but still not instantaneous. Fast-moving subjects can appear to bend or skew, which is called the jelly effect. Cameras with global shutters or very fast sensor readouts minimize this problem.

Color temperature from artificial lights can cause issues in high speed video. LED lights and fluorescent tubes flicker at the mains frequency, which is 50 or 60 Hz depending on your region. At high frame rates, this flicker becomes visible as brightness pulses in the footage. Always test your lighting before shooting high speed. Use flicker-free LED lights or tungsten lights that do not flicker.