Re: remote control photography - sort of

On 18 July, 23:16, David Reid <da...@xxxxxxxxxxxxxxx> wrote:
bobharvey's best pigeon dodged hawks and farmers' guns to bring me the
following:



On 18 July, 21:45, David Reid <da...@xxxxxxxxxxxxxxx> wrote:
Not photos taken by remote control, photos of remote controls.

Every digital camera I've played with can see far enough into the
infrared range to clearly see the IR LEDs in remote controls, which is
handy if you're trying to jaybex out if it's the remote or the device
you're pointing it at not jaybexing.

The thing is I'd expect them to show up on the camera as deep red but
they don't, they always show up as blue-white, can anyone explain why
this is?

Hmm.

IR filters are fitted to most cameras to confine input to the visible
spectrum.  I suspect that all the pixels are sensitive to some extent
to IR, and shining a laser down their maw saturates all of them, not
just the red ones.  Hence the colour.

I don't think IR remotes have lasers in them, and they look blue-white
no matter how dim they are. Seems from other answers though that the IR
filters aren't actually that good and the colour filters don't block IR
at all.

They have LEDs. LEDs do not lase, 'tis true. But they are
monochromatic, Have quite a narrow beam angle, and can produce light
that is close to coherent. (there is a coherence gradient from the
centre to the edge of the beam)

Even taking them hundreds of microfurlongs away won't make them 'dim'
in the same way as e.g. a candle.

Some have diffusing lenses , true. But most are powerful enough to be
used pointing 180 degrees away from the TV, so that the signal has to
bounce off the decorations
.

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