Why do surveillance camera's look like they're raining in infrared?

I have 3 outdoor security camera's that switch to infrared during the night. They are motion detected so its extremely annoying that they detect what looks basically like heavy rain at times... but nothing is going on outside. I am not sure what it is? Is it just invisible dust only Infrared can see? Other outdoor cameras don't have this problem....?

3 Answers

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  • L
    Lv 7
    3 weeks ago

    I have had a similar issues with outdoor security cameras over the last several years - interestingly, there are the same model camera and seem to pick up fog or other airborne moisture... The best I can figure is the angle of the camera matters. When the lawn & flower bed sprinklers go on early in the morning, one security camera looks like it is snowing or foggy - the rest don't and the only difference is their angle to "horizontal". It is how the infrared from the camera reflects against the aerosolized moisture...

  • qrk
    Lv 7
    3 weeks ago

    The "rain" you see is probably noise (Johnson noise and sensor quantum noise). The gain of the camera is turned up to maximum when in IR mode. It is akin to turning up the gain to max on a audio system. The hiss you hear is electronic noise.

    The false positives are most likely due to other things like insects flitting about and branches moving in the wind. I had a thermal IR sensor that kept on tripping. Moths flying in front of the sensor would block the sky which registered a large temperature change (sky looks very cold, moth is slightly above ambient temp).

  • BriaR
    Lv 7
    3 weeks ago

    All night-time IR security cameras I have ever used detect "unwanted" movement. Trees blowing in the wind, heavy rain, spiders making webs across the camera housing all trigger the movement sensors. Just wait till it snows!!!

    Depending how sophisticated your system is you may be able to adjust the sensitivity but I always worked on the principle of, better a few false detections than missed intruders!

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