You recorded it and saw nothing. Could you have seen it?

A single black flicker frame on a 60Hz display is visible for about 17 milliseconds. Record at 2fps — a sample every half second — and it lands in a frame about one time in twenty-nine. So a clean recording is the overwhelmingly likely outcome whether or not the flicker is there, and “we recorded it and saw no flicker” is a true sentence that is not evidence of anything. That gap is arithmetic, and it is knowable before you spend the capture rather than after.

The calculator is free and needs no account. Write down what you are recording and what you are recording it in order to see — each thing with how long it is visible — and the odds come back per line, with the minimum frame rate that would settle each one and which channel it needs. Never-happens claims are treated as the asymmetric case they are: seeing a thing once needs one lucky sample, but saying it never happened needs coverage that could not have missed it. Every lane ships a worked example that costs nothing. Writing the report needs credits.