Light Flash

A burst of light overwhelms the frame for an instant. Detail disappears, then comes back, and the audience feels the interruption before they identify it.

It works as punctuation. A flash can mark an impact, a memory arriving, a camera firing or a cut you would rather the audience did not see cleanly.

Exposure is pushed past the top of the range for a small number of frames. Highlights clip to white first, then the mid tones follow, and the picture flattens out as it goes.

The recovery is what sells it. Real exposure comes back through the mid tones as the light falls, so the frame returns in stages rather than switching back on.

Duration matters. A flash of two or three frames reads as an event. Anything much longer reads as a badly exposed shot, which is the difference the entry note is pointing at.

A rolling shutter complicates it. The sensor reads out line by line, so a flash shorter than one readout lights only part of the frame and leaves a bright band across it. Global shutters and film do not do this.

Use it on impacts, on gunfire and lightning, on a photographer working in frame, and to hide a join between two pieces of footage.

Leave it out of anything that has to be watched comfortably. Repeated flashes are hard to look at, and some viewers cannot watch them at all.

Lens flare is an artefact of the glass, and it leaves shapes and streaks while the exposure of the scene stays broadly correct. A light flash changes the exposure itself, so the whole frame blows out together.

The test is whether the picture survives. In a flare you can still read the scene around the artefact. In a flash there is nothing left to read for a moment.

The frame blows out and stays blown out. Say the exposure recovers, and say how quickly, because a flash with no return is an overexposed shot.

The other failure is a slow fade up and down, which reads as a dissolve. Ask for a hard falloff after the burst rather than a gradual one.