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Comment by admash | Hacker News Reader

Presumably this could be used for color imaging by using lasers of different wavelengths?

If it’s truly just like the methods astrophysicists use for transit imaging, you might even be able to do some funky stuff like monitor invisible gasses. Could potentially be revolutionary for things like fume safety and viral spread tracking, among other uses. Might even be able to analyze liquids in a container without having to touch the liquid (the name for this type of testing evades me at the moment)

I believe it'd be pretty wonky coloring, or at least it could be, since it'd be capturing snapshots of individual frequency responses. If something is visibly green, reflecting across most of the greenish areas of spectrum, but happens to absorb the exact frequency of the laser, it'd appear black when imaged this way. Or at least not green.

I think that’s the case for regular cameras too though, the filter for the pixels doesn’t exactly replicate the response of the cones in the eyes either, right? So you have things where the camera sees a different color than a human eye.

Regular cameras respond to a wide range of wavelenghts, and they do actually reasonably mimic the response of the human eye.

Either way, it's the "range" vs "single wavelength" that's key here. The green band (or blue band or red band) isn't one wavelength. It's an average over a fairly broad range. Single-wavelength (or very narrow range) images are quite different.

A fun example of these effects is "black fire".

https://www.youtube.com/watch?v=F0LWtieip9E

Take a photo of the sun setting behind clouds, and then marvel that the camera still sees a big red Sun, when your eye barely sees it. That's because the camera goes way farther into the red than your eye, and the clouds let that sub-red through.

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