Motion activated but no motion in video

[REIGNINSLAYER]

I have an outdoor camera under a patio. The camera is not exposed to weather. Every so often I get daily motion alerts on the one camera. I view the recorded files and there is no motion. One common variable is it appears there is 1/2 second flash on each video at the beginning of each file. Do I have a camera going bad? There are no external lights flashing around or at the camera.

[jguerdat · Accepted solution]

Could be lots of things like a bird flying through, a cat walking just out of sight, etc. The inherent lag in the system means things may not be seen since they move out of view before being able to be recorded.

[Geoff]

I've noticed that a moth can trigger the camera.

[KD808]

I would bet that whatever set off the motion was long-gone before the video capture started. 

[Hekmen]

I have the same issue with my cameras. Does anyone have an answer for the flash of light at the beginning of the recording?

[jguerdat]

I have some flashes like that and just put it down to the way the sensor reacts when starting up.

[Hekmen]

Yeah but what is the sensor sensing? There is nothing on the recorded video. There has to be a reason this flash is occurring.

[jguerdat]

I don't think it's sensing a flash of light but rather that it's something in the startup of the sensor and associated circuitry that allows a brief overexposure to be recorded.  It would seem to be able to be fixed by the camera firmware but perhaps not.