5MP 2CD2T55 Face detection feature

[unbahlievable]

I just picked up a 2CD2T55F-I8 with 6mm lens from EBay and I'm wondering how face detection works.

I have it perched under the eave of my garage pointing out the driveway and I'm
walking in front of it looking into the camera from about 10ft away. It does not alert of
any face detection or from anyone else who happens to look at the camera from the sidewalk
further out about 30ft.

However, it was sending face detection events one evening when the driveway
was wet from rain. I guess it was picking up the light reflections that looked like
facial features (none that I could make out)

Anyone else play with this?

thanks