Overall lighting level changes

hugh_fraser · Post by **hugh_fraser** » Tue Apr 03, 2007 4:04 pm

I have three outdoor cameras with motion detection enabled. Yesterday had broken cloud cover moving quickly, which created cloud shadows that changed the ambient lighting frequently. The result was several hundred events in Zoneminder, and the stills clearly showed that there was in fact no motion in any of the monitored areas, but the background lighting changed continuously and was identified as changes. I'd like to adjust Zoneminder to ignore this effect, but don't know what parameters to change. There are some characteristics of the changes detected... they're usually large blobs like a wall that don't move between frames. The change in lighting persists for a few seconds, then returns to its original state after the cloud passes. So is this something that can be modelled in Zoneminder and ignored without sacrificing the detection of real motion?

ammaross · Post by **ammaross** » Thu Apr 05, 2007 10:01 pm

You could try setting up a small preclusive zone high on a wall and configure the pixel threshold depending on the lighting change you expect.

I had a camera that the video feed would distort briefly every minute or so, and only at the very bottom few rows of pixels, but it was enough to trigger an event. After setting up a very small (62 px) preclusive zone, and setting the pixel threshold to 20, it blocked these blips from recording. The same idea should work for you with lighting changes.

Post by **zoneminder** » Sat Apr 07, 2007 7:28 pm

There will be an additional option in the next release for a zone to inactivate itself for a given number of frames if a 'max' threshold have been exceeded. This should help in your case but the suggestion by ammaross is a good opne and what preclusive zones were designed for.

hfraser · Post by **hfraser** » Sat May 05, 2007 5:58 am

OK. I have created a preclusive zone on the wall. Unfortunately, on days like today where there's been a lot of cloud movement, I'm missing real events if a cloud happens to pass over at the same time. Is there a way to configure Zoneminder to ignore objects that do not move from frame to frame (like a wall that's suddenly brighter). The blobs that appear in the frames generally do not move, since they're stationary objects whose intensity has changed. I need to ignore those while still remaining sensitive to motion. I do recognize that motion is detected as the deltas between frames, so perhaps there's a way to configure a preclusive zone that can be "over-ridden" by significant motion in another zone, such as a doorway or sidewalk.

ammaross · Post by **ammaross** » Mon May 07, 2007 3:37 pm

You could tag areas that "do not move from frame to frame" as Inclusive zones and use Active zone(s) in the area that you would normally see real motion. That way a lighting change on a pillar would only cause an event if there was also an event triggered by at least 1 one Active zone.