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Comment by hammock

11 hours ago

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).

    • Yes and no. The IR filter is pretty strong. If you have an intense IR source, then it overwhelms the filter, but it would blow out the sensor, without it. The sensor is biased towards IR.

      I've converted cameras (DSLRs) to IR, and you use a replacement IR-pass filter. The IR-blocking (default) filter looks like a piece of blue glass. The IR-pass filter looks like a piece of black glass.

      NOTE: It's not perfect. The DSLR image processors and calibration systems are calibrated to the IR-blocking filter. Stuff doesn't work the same, once you convert.

      2 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.)

  • 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.

    • I pointed at the remote of my fan and I can see it. I am on 15 Pro. However, as the sibling comment said, it is very faint so I'd guess not very realistic.

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.