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Comment by bb88 | Hacker News Reader

So interesting facts about that camera.

Most cameras have an IR Cut filter which acts to block IR light from the camera. This prevents IR light from flooding the sensor giving the image a red hue.

For astro photography IR light is useful. Hydrogen gas in nebulas can emit IR light. The human eye can't see it, but the camera sensor (without the IR Cut filter) can, and will be sensed as red light.

If one adds a visible light filter to the front of the camera, then the camera can take images of IR spectrum only.

Nikon and Canon both sell cameras without the IR Cut filter. Also third parties have been able to remove the IR Cut filter on existing camera bodies.

View on HN

It works even on cheap webcams. Remove the piece of blue glass and replace it with the black plastic that covers the ir leds from an old remote.

I have one where I just removed the filter and added some IR led's for my 3d printer cam, that way I don't need visible light and the room can stay dark if I need it to be.

I did it back enough in the day that I used a negative from getting pictures developed. I think I got the idea in Hardware Hacking Projects.

I did the same too, but funnily enough I stumbled upon it by accident when I was trying to find things that pass IR through but not visible light (like coke, sunglasses, ink etc.) using my Sony camera with nightvision mode. I was on a quest to get "x-ray vision".

Phone cameras can often see into the IR spectrum, but by now most of them are able to deal with that properly to make the images look normal. I remember some 3MPix phone camera from like 2008 that created strong purple coloring for example with camp fires, especially if you took images of the embers (also with BBQs if done with charcoal). Just hold an IR remote and press a button on it and see if your phone sees the IR LED light up. My current smartphone sees it clearly. No idea how far into IR the A7s sensor without the IR filter goes; with IR filter it barely registers my IR remote (I have an unmodified A7s). It also depends on the glass/lens.

You can also buy Raspberry Pi cameras in the "NoIR" version that comes without the short pass filter, or do an easy DIY conversion in the case of the RPi HQ camera.

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