How slow is 120fps played at 24fps?

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.

What shutter speed should I use for 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.

Does slow motion affect quality?

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.

How much light do I need for slow motion?

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.

PhotoCalcs

Slow Motion Calculator — Playback Duration

Calculate slow motion playback duration, slowdown factor and recommended shutter speed.

Shooting Frame Rate

Frame rate your camera records at (e.g. 120, 240)

Playback Frame Rate

Timeline frame rate for playback (e.g. 24, 25, 30)

Real-Time Duration

How long the real-world action lasts

How We Calculate This

Slowdown Factor

Factor = shooting fps / playback fps

Playback Duration

Playback = real duration x slowdown factor

Recommended Shutter

Shutter = 1 / (2 x shooting fps)

Frequently Asked Questions

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Last updated: February 2026

All calculations are estimates based on standard optical and photographic formulas. Results may vary with specific equipment.