On Tue, 20 Jun 2017 11:27:27 -0400, Frank Krygowski
wrote:
Motion-activated lights indoors would make that surveillance camera a
lot more useful!
Not really. The problem with aiming a motion activated surveillance
camera through a window is that everyone that passes by sets off the
motion detector. The better DVR (digital video recorders) have
programmable zones. The viewing area is chopped into small
rectangular zones, each of which can be set to detect motion or ignore
motion. This helps, but is far from perfect. Something like this:
http://surveillance.aver.com/Images/Shared/IMD%20revised.jpg
where only the door areas detect motion.
The big problem with camera placement is the field of view usually
ends up many times wider than a person's head. My guess(tm) is the
camera field of view at the window was probably 20 times the width of
a person's head. If the camera was a better quality 1920x1080, the
persons head would be only:
1920 / 20 = 96
pixels wide. Try to identify someone from a photo where the person's
face is only 96 pixels across. Here's me at 660 pixels across:
http://802.11junk.com/jeffl/pics/jeffl/slides/jeffl-07.html
and at 96 pixels across, expanded to the same image size:
http://802.11junk.com/jeffl/pics/jeffl/jeffl-07-96.jpg
96 pixels across actually looks fairly good, but only under ideal
conditions. Add to that the distortion caused by positioning the
camera at about 45 degrees downtilt near the ceiling, marginal night
time lighting, and a possible disguise.
Also, the same camera would easily produce a recognizable face photo
if the field of view was reduced to perhaps 5 times the width of a
person's head, but then the field of view at the front window would be
too small to be useful and require multiple cameras to cover the
entire window.
Incidentally, my favorite mistake is to put cameras on the ceiling,
which usually produce great a video of the top of the burglars head,
hat, or hoodie.
--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060
http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558