Objective Evidence

This weekend, at Balticon (the Baltimore Science Fiction Convention) I got to play a bit with an infrared-sensing webcam. These turn out not to be very difficult to construct, because CCDs are sensitive well into the IR range. The normal filter blocks IR but passes visible light; by replacing it with fully exposed film stock, which is opaque to visible light but transparent to IR, you get infrared imaging.

The output was rendered live on a laptop as a mostly black-and-white image with occasional pale pseudocolors. The camera-builder explained that under daylight or artificial-light conditions, most of what you see is actually reflected rather than emitted IR; these light sources emit plenty of heat. (Someone demonstrated by pointing an IR remote control at the webcam that you can in fact see emitted IR. Hold that thought, it will be important when we reach our punchline.)

In fact, he claimed that human retinas have some sensitivity to IR that is normally swamped by the response to visible light; with the same film-stock trick done on a pair of welding goggles (he claimed) you can go outside on a bright sunny day and see in infrared without electronic amplification or frequency-shifting.

It’s a different world, though, because IR reflectance and color don’t correspond well to visible-light reflectance and color. My black T-shirt, the one one with the mock MPAA rating on it reading “XYZZY – WARNING: FULL FRONTAL NERDITY – Tech-Challenged Persons Strongly Cautioned”, appeared pale green. A bystander commented “That’s how you tell the real Goths from the fake Goths.” I of course rounded in him in mock indigation, because what self-respecting geek would want to fake being a Goth?

Then we turned the camera on my wife Cathy, who was elegantly turned out in a black cami tank top, a black blazer, and a titillating amount of visible skin. The tank-top looked dark in the image, but the blazer was a shade of white a few degrees blue-shifted from her skin tone, and seemed to glow as though by specular reflection or emission rather than diffuse reflection.

“Hmm. I wonder why my jacket looks like that?” asked she.

I saw my moment. “Because,” I intoned, “you are a hot chick.”

14 thoughts on “Objective Evidence

  1. >I of course rounded in him in mock indigation, because what self-respecting geek would want to fake being a Goth?

    I like Joy Division and Bauhaus, but that’s about as far as it goes. (Seriously, Ian Curtis was the voice of God.)

  2. My jocular point was that while I suppose a geek might incidentally be a goth, a geek wishing to fake gothicity seems unlikely.

  3. Well player, sir, well played. Such opportunities are rare, and must be recognized and seized when they present themselves — which you did admirably!

    I don’t know if Heinlein ever said it, but he shoulda: “Never pass on an opportunity to flatter your wife in public.” Or in private, for that matter.

  4. Daniel Ash/David J aren’t bad, either.

    The camera-builder explained that under daylight or artificial-light conditions, most of what you see is actually reflected rather than emitted IR; these light sources emit plenty of heat. (Someone demonstrated by pointing an IR remote control at the webcam that you can in fact see emitted IR.

    Harrumph.

    Infrared videography (nor IR photography) is not the same thing as thermal imaging. Thermal imaging is the night-vision video technology used by the police and sensationalist TV shows. Thermal imaging systems are capable of detecting different wavelengths of IR energy than the system you used, (and are at least an order of magnitude more expensive.)

    The objects that show up on this camera must be illuminated by an IR source – the sun, a light bulb or even a camera flash. Most objects (trees, people, hills, etc) do not radiate IR energy at wavelengths which can be recorded by IR-sensitive devices. The camera you were playing with is unlikely to be sensitive enough to record IR from most heat sources.

    So, rather than Cathy being a “hot chick”, she was simply a *reflective surface*, but that wouldn’t have scored the same points.

    BTW, by definition, ‘light’ is that portion of the EM spectrum that is visible to the human eye. As such, “visible light” is redundant.

  5. If you don’t have any exposed film handy, try turning out the lights and pointing your camera at the window of a remote control while operating the control.

    Some (but not all… probably depends on the low-light sensitivity of the camera and the quality of its IR filter) will let you see the pulses from the remote in the camera viewfinder.

  6. I’ve seen plenty of video from normal video cameras that clearly detects IR from remote controls and shows it as visible light, without the need (or desire, since it’s generally an accident/coincidence in these cases) to manipulate the ambient lighting to do so. Not a subtle effect, either…the IR LED at the end of the remote shines like a beacon on video when a button is pressed. Some (most, now?) cameras probably have filters on the lenses to prevent this, but perfectly ordinary camcorders not priced or marketed specifically for low-light work (let alone IR sensitivity) have shown this effect.

    And whether IR source or merely efficient IR reflector, esr’s wife is very definitely a hot chick. :)

  7. “My jocular point was that while I suppose a geek might incidentally be a goth, a geek wishing to fake gothicity seems unlikely.”

    Don’t tell me you can tell fake goths from “real” ones :-) The whole phenomenon is so superficial in 2009 that “real” has little meaning.

    I mean in the eighties, early nineties, it was really good, because they could make great stuff like this (in 1989)

    http://www.youtube.com/watch?v=HXUcwdXEtm4

    … you can put with some silly clothes and black makeup in exchange for such good music and pics (borrowed from GITS), I suppose. Goth/darkwave/industrial/EBM made a lot of contribution to the development of electronic music. But now? Goths in 2009? C’mon…

  8. Agreed on the flattering of the wife. Works especially well to get her in the mood, at least IME.

  9. Why would a nerd want to fake gothicity?

    Why, because he could, of course.
    You sir, have just hacked clothes.

  10. IR photography has been around for a couple of years now. I find the pictures to be fascinating and beautiful.

    Do a search in Google Images for “ir photography” just to get started!

  11. My mother drew a distinction between achievement and success. She said that ‘achievement is the knowledge that you have studied and worked hard and done the best that is in you. Success is being praised by others, and that’s nice, too, but not as important or satisfying. Always aim for achievement and forget about success.’

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