Face detection works properly if cameras are installed and set up as follows:

1. The maximum angle of incidence should not exceed +/- 15 ° off the ground level.
2. Distance between pupils on the received photos of face must be not less than 50 pixels.
3. Position the camera to minimize the chances of overlapping faces in FoV.
4. The faces in FoV must be evenly lit.  No directed side illumination.
5. Face shots from cameras should be clear. No image blur caused by human motion.
6. Contrast range of a human face on camera shots must be at least 64 shades of gray.  No insufficient or excessive lighting.