Mike Burr - log

[comp] Observe and Report

It seems like surveillance cameras should, as a matter of security, make a point of analyzing and storing content that only a human eye could conceivably perceive.

For example, if a surveillance camera picked up just a bit of IR and this ended up "on disk" mapped to a human-perceivable color, it could affect the trustworthiness of its output (video files and/or video analysis).

No doubt this has been thought of, but I wonder...

If you really really wanted to, what could/would you do to cause something (anything you like) to end up on disk but for this something to not be perceivable by other people.

Just to be lazy, let's suppose that the human eye has a gap in perceiving a certain "band" of wavelength. You could paint a sign using ink whose color lands somewhere in this invisible band and have ONLY he camera perceive it.

Contrived example:

You notice someone sneaking out of Lowes with a bag of concrete. As a conscientious citizen, you grab a big poster board and your human-invisible marker and make a sign with an arrow to let the camera know, "Hey, that guy's got a bag of concrete down his pants!!"

A better example is left as an exercise.

If not "a band" then how about a very carefully selected compound color choosing the human weak points as "notes"?

Are there real examples of this? Short of just blinding the camera, could you conceal yourself? Maybe by pointing the right kind of (not visible to humans) flashlight at your face?...

Not a thing? Maybe another trick:

Say you can create a flash of arbitrary brightness and of arbitrary duration.

If you tune your flash so the duration is very very short but the brightness is very very high, and this results in X photons hitting the sensor, would that be "seen" (brightness) as the same by the sensor as a longer flash that resulted in the same number of photons, X, hitting the sensor? (We assume all of these "flashes" have a duration shorter than the duration of a video frame.)

"Probably", is my best answer.

Now, does the human eye work the same way?

"Probably not", is my guess.

I think there's a way to make a flash of duration that's short enough that the eye would not perceive it, or at least as easily make sense of it.

If not bullshit, this would be another possible path toward inconspicuously (to standers-by) deceiving the camera system.

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