180-degree shutter rule

Shutter speed should be double the frame rate (1/50 at 24fps) to produce motion blur that matches human vision. Needs stabilized footage — on shaky action cams the blur smears, on a gimbal it reads as cinematic. Outdoors this forces ND filters to hold ISO 100.

Where it stops applying: on digitally-stabilized action cams the rule actively backfires — see action-cam-shutter-exception, where philip-carneiro shoots 1/200 fixed on the bike because RockSteady needs sharp edges to track. gerrit-knein's 1/50 works precisely because a gimbal stabilizes mechanically. Match the shutter to the stabilization method, not to a number.

Sources: Gerrit Knein / Pocket 4P, Philip Carneiro / Action 6