I read the technical explanation in the Blink Support section about how the motion detection uses IR to detect moving objects. This is not my area of expertise, but if it only detects moving objects and not images, why do my cameras keep getting set off every time the wind blows and the shadows of leaves move? Wouldn’t a quickly moving shadow be somewhat invisible to infrared?
Google has your answer.
Study the part about emmiter vs. reciever
Study the part obout the heat signal differential between emmiter and reciever
A shadow would create a differential in passive infrared reflected heat signature. Amount of heat before the shadow vs. after the shadow. The differential change = activate the PIR sensor circuit.
In all of it, remember PIR sensor does not detect motion. However what it does detect is often times related to something moving. Hence why it is called a motion detector and used in cameras and flood lights.
If you want to put the engineering hat on…
Go to https://www.digikey.com/ and look up PIR sensors.
Pic below is the Blink circuit board