Comment by baking
10 hours ago
But then you would need an IR camera instead of using the phone's camera. An IR camera should be able to find some hidden cameras passively by detecting a heat source.
10 hours ago
But then you would need an IR camera instead of using the phone's camera. An IR camera should be able to find some hidden cameras passively by detecting a heat source.
There are SWIR, MWIR, and LWIR cameras among IR cameras. SW is just regular camera with the filter removed and they can't see heat. Somewhere between SWIR and MWIR are uncooled IR cameras that use MEMS heat sensor ish arrays built on top of a camera sensor that can actually see heat by differentiating between previous and current frames, with the caveat that they cannot do it indefinitely but must use a mechanical shutter to periodically cool down to operational conditions.
MWIR and LWIR cameras are often cooled and uses more exotic sensing mechanisms, sometimes even vacuum tube based, nowadays usually semiconductor based but not regular CMOS. Some require mechanical shutters obscuring view every other frame(that, I think, is where BHOT/WHOT switch came from; it must be switching whether to show odd or even frames).
You need the MEMS types or better to see heat; they're more often referred to as thermal cameras than IR cameras. They are also unable to see through regular soda-lime glasses, that might pose its own challenge as well.
Can’t phone cameras pick up IR?
the raw sensor can, but there's usually an IR blocking filter in the lens assembly.
not really, no. It'll happily show you IR (just point it at your remote control with the camera active, and press some buttons. Enjoy the light show on your screen that your eyes don't see).
3 replies →
I’d think so. My iPhone can see my remote’s IR.
It sees it poorly. IR is deliberately (though imperfectly) filtered in the optical path.
The dim purpleish glow from a remote that is seen through [many] digital cameras would be quite bright if this IR filter weren't in place.
It doesn't have to be that way, but it usually is that way anyway -- as a design intent.
Cameras used for surveillance, meanwhile, often lack these filters. They're designed with more of a focus on getting any kind of image at all, including when working with infrared illuminators in the absence of visible light. Some even have mechanical elements that move filters out of the optical path for night mode.
This differs tremendously in comparison to a camera that is designed to produce very beautiful visible-light photographs.
(This all conspires to mean that IR is kind of a non-starter for this sort of cell phone camera hack.)
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That was true years ago, but I haven't been able to use an iPhone camera to pick up an IR signal in a long time. Just tested it to be sure they hadn't reverted to an unfiltered lens (17 pro) and nope, no IR visible.
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Depends on how cheap you go - most of the cheap ones that take images where the blacks look grey likely do not have an IR filter on them. Most quality phones will use a camera with IR filters on them - blacks look like blacks.