[genewitch]

A hat with infrared LEDs aimed out, such that there was a torus of light around your face. Invisible to humans (generally), only visible to cameras.

It won't "work right" on cameras that have permanent IR filters. Maybe. I haven't tested this in years.

I have a feeling that IR of the correct strength and frequency would be dimly visible to humans, though. Similar to cameras with monochrome night vision via IR LED.

[bsenftner]

One only needs 1 or two LEDs near their face, but they need to be blinking in short irregular intervals. Cameras have mechanical controls for controlling focus and the amount of light they capture, and that can be attacked with these irregular blinky LEDs that cause the camera to try to adjust to the bright illumination from the LED, but then it is gone before the adjustment is complete, but then it is on again, then off again. The result is a person that never is more than a grey silhouette.

I worked in enterprise FR, on one of the globally leading systems, as the lead developer. That scenario defeats pretty much all FR when from a single camera. It can be mitigated with multiple camera views, which few FR systems are setup for multiple quality views at every key location.

[nhecker]

Interesting. I bet a candle-flicker LED or two in series would add a nice bit of random (or psuedo-random LSFR?) AM noise to the IR LEDs.

[TeMPOraL]

That would only maybe work for automated tracking; if someone wants to get the image of your face, they should be able to do it in post, unless the recording quality is shitty - the tiny variations in brightness might contain just enough information to reconstruct the face shape with a little filtering.

(Now I wonder, how narrow-band such IR LED is, and if it could be made to emit a single frequency so sharp, it would create funny diffraction patterns off cameras' surfaces and lens imperfections, clobbering the high-frequency components of the image...)