Slow Motion Calculator — Playback Duration

120/24 = 5x slower. A 2-second real-time event becomes 10 seconds in playback. 240fps at 24fps = 10x slower. 960fps (some phones) at 24fps = 40x slower. Higher shooting frame rates produce more extreme slow motion.

Follow the 180° rule: shutter speed = 1/(2 x fps). At 120fps use 1/240s. At 240fps use 1/480s. This maintains natural per-frame motion blur. You will need strong lighting or wide apertures due to the fast shutter speeds required.

Many cameras reduce resolution or bit depth at high frame rates. A camera that shoots 4K at 30fps might only do 1080p at 120fps. Some cinema cameras maintain 4K at 120fps but they are significantly more expensive. Check your camera specs for resolution at each frame rate.

High frame rates require fast shutter speeds, which reduce light. Going from 24fps to 240fps with 180° shutter rule changes shutter speed from 1/48s to 1/480s — a 3.3 stop light loss. You need roughly 10x more light for 240fps than 24fps, or must increase ISO significantly.