Review motion for flashes and abrupt visual change

A flash review concerns rapid changes such as alternating bright and dark frames. A motion review also considers sweeping zooms, large translations and parallax. These are related viewing concerns but are not interchangeable tests. A sequence with no flashing may still contain uncomfortable movement.

W3C’s Three Flashes or Below Threshold criterion addresses flashes more than three times in any one-second period unless the general and red-flash thresholds are satisfied. The threshold definitions matter; do not reduce the guidance to a claim that any three flashes are automatically safe. Use the current source and a suitable assessment workflow.

For each candidate event, record file version, scene, start and end time, frame references, observed behavior, approximate affected region, proposed replacement and retest status. An illustrative log entry could be: “Scene 3, around 00:12: alternating full-frame bright transition; replace with a steady neutral hold; assessment pending.”

This is an example of a record, not a finding from an actual rendered clip. Do not mark it passed until the replacement exists and the encoded result has been inspected. Record uncertain events as uncertain rather than inferring safety from the project’s effect settings.

Replace a decorative flash with a cut, a stable color hold or a small local emphasis where appropriate. Replace a sweeping camera move with a labeled overview followed by a static detail. The replacement must preserve the transition’s purpose: new subject, elapsed time or continued action.

Do not simply lower an effect’s opacity and assume the issue is resolved. Compositing, background brightness and the area affected can change the final result. Likewise, slowing a move may extend exposure to motion without improving the explanation. Compare alternatives in the actual composition and retain the one that communicates clearly with less unnecessary disturbance.

Inspect the revised export at the event and across neighboring cuts. An effect removed from one scene can still leave a bright one-frame discontinuity at the join. Use frame inspection for defects and the appropriate analysis method for threshold assessment; a casual watch-through is not a certification.

Keep user-controlled playback and any restrained-motion alternative in the delivery plan. W3C’s interaction-motion guidance concerns the hosting web experience as well as design choices. Record who reviewed what, which tool or method was used and what limitations remain. Avoid publishing a blanket “safe for everyone” or “WCAG compliant” statement from this narrow production check.