What changes on the camera when adjusting Motion Detection?

[EyeInTheSky]

I'd like some technical information on how the cameras are affected when adjusting the motion detection sensitivity.  What is being changed when we turn the percentage down?  Don't just reply with a link on adjusting the camera sensitiivty, etc. because these articles don't answer the questions I'm posting here.  Also, it appears that these cams don't pick up only thermal detection i.e. body heat.  It seems that they pick up anything that movies in front of the cam.  Can you please confirm if this is correct?  I have two cams mounted outside.  One in our front entryway, where the cam overlooks the entryway and the walkway out to the sidewalk and the street.  The other cam is mounted on the corner of the garage where the camera overlooks our driveway, front yard and the street.  Initially, I set the cams up for 100% motion detection and began getting alerts for every car that passed by the front of our house.  Turned it down to 90% and the alerts were reduced considerably but still getting some alerts when cars passed in front of the house.  Just turned it down to 85% and no alerts yet.  What I don't want though is to turn the sensitivity down so low that it doesn't pick up motion that it should be picking up.  I also have the cams mounted upside down with the lenses inverted, so the motion sensor is "on top" as opposed to on the bottom.  Does having the motion sensor on top reduce the effectiveness of the motion detection?  It doesn't appear so but I would like someone to confirm on this as well.  If any of the Netgear support staff happens to be reviewing my post, please note the following:  The Netgear mounts I purchased have photos of the cameras mounted upright, as do the instructions, but there are no warnings about mounting the cams upside down, or suggestions on doing so.  So the user is sort of led to believe that they shouldn't be mounted or used upside down, nor is any information given to the contrary.

[southerncuban]

I am not an expert but I have found through trial and error that the cameras work best upside down when mounted up high looking outward (across a room
Or covering a larger area). On the other hand, I have found that if you have your cameras mounted up high facing down (more of a birds eye view for a smaller area) they pick up motion better when mounted right side up. I have my sensitivity set to 90% and the rain set it off. I lowered the sensitivity to 80% and when my tree blows it sets it off. I'm going to try to reduce it to 75% and will let you know what happens. I wish I had more answers for you!!

[TomMac]

I'd like some technical information on how the cameras are affected when adjusting the motion detection sensitivity.  What is being changed when we turn the percentage down?  

You are lowering the "trigger point" on the PIR ( passive infrared sensor )  making it less sensitive ( less likely to record )

 Also, it appears that these cams don't pick up only thermal detection i.e. body heat.  It seems that they pick up anything that movies in front of the cam.  

The PIRs do not pick up body heat.... they detect the infrared radiation OR the reflection of same.

.  Initially, I set the cams up for 100% motion detection and began getting alerts for every car that passed by the front of our house.  Turned it down to 90% and the alerts were reduced considerably but still getting some alerts when cars passed in front of the house.  Just turned it down to 85% and no alerts yet.

Setup is a trial and erro process, esp when outside ...80 to 95 % will prob cover most user.

Hints, 1)try not to cover to much area, 2) have it sort of pointed down and use the max detection range of about 25 ft, 3)cars do give off a lot of IR and do trigger many false alerts so try not to cover a roadway ( unless you want to) 4) the PIRs appear to be more sensitive on the edges and also better to cross ing the field of view.... so setup should apply many of these

I also have the cams mounted upside down with the lenses inverted, so the motion sensor is "on top" as opposed to on the bottom.  Does having the motion sensor on top reduce the effectiveness of the motion detection?

To my tests, it doesn't make much diff...but there have been a few users that flipped the cam for mounting and using 'shields' over the PIR to make it function better

but there are no warnings about mounting the cams upside down, or suggestions on doing so

The only thing I would say is, if your going to mount it upside down, make sure battery door o-ring is in its small groove and apply some silicon gease to assist in making the unit more water resistant. Another user mentioned he put tape over the bottom to help sealing

If you can find his thread you could ask him directly in a PM