180-degree Shutter Rule
The convention of setting the shutter speed to roughly double the frame rate, producing motion blur that reads as natural.
Formula / rule
t ≈ 1 / (2 × fps)
Measured in
seconds
In depth
Too little blur and movement strobes into a stuttering, hyper-real look; too much and it smears. Half the frame interval sits where audiences have been trained by a century of cinema to see motion as normal. Deliberate departures are expressive choices — a narrow angle for jarring combat, a wide one for dreamlike drift.
Examples in practice
Shooting 25 fps at 1/50 s gives natural motion; the same scene at 1/500 s produces a harsh strobing effect.