Frame rates & the 180° rule
24, 30, 60, and 120p on this body, the shutter that makes motion look right, and the 4K120 crop.
- Choose a frame rate for the look and the purpose
- Apply the 180° rule to set a natural motion-blur shutter
- Account for the 1.58× crop when shooting 4K120
Video adds time to the frame, and frame rate is how you slice that time. The number you pick shapes both the feeling of the motion and what you can do with it later.
The rates and what they are for
- 24p — the cinematic standard. Slightly stroboscopic, dreamlike, the default for anything that wants to feel like film.
- 30p — a touch smoother; common for straight, informational video.
- 60p — smooth and lifelike, and it can be slowed to half speed in a 24/30p timeline for gentle slow motion.
- 120p — for dramatic slow motion, playing back at a fifth of real speed.
Start at 24p for most storytelling. Reach for higher rates when you know you want smoothness or slow motion.
The 180° rule
Motion looks natural when the shutter is open for about half of each frame’s duration — the 180° rule. In practice: set your shutter to 1 over twice the frame rate, snapped to the nearest real speed:
- 24p → 1/50
- 30p → 1/60
- 60p → 1/125
- 120p → 1/250
Too fast a shutter makes motion look stuttery and video-game sharp; too slow and it smears. The rule keeps blur looking like the movies.
Keeps the 180° shutter for natural motion blur instead of raising it in bright light.
Here is the catch the helper solves: in daylight, that slow shutter lets in far too much light. You cannot speed the shutter without breaking the look, so you cut the light with an ND filter instead. Dial your frame rate, light, and aperture and it tells you how many stops to remove.
The 4K120 crop
High-speed modes cost field of view. Recording 4K120 applies a 1.58× crop on top of the sensor’s own — so your 10mm becomes roughly a 24mm equivalent, and your 10-20mm zoom behaves like a 24-47mm. Plan for it: if you want wide slow motion, you will be at the widest end of the Sony and still not as wide as usual.
In the field
Shoot the same passing motion — a hand waving, someone walking by — at 24p with 1/50, then at 24p with 1/500. Play them back. The first looks natural; the second looks oddly crisp and stilted. That difference is the 180° rule earning its keep.