Looking at the image then,robi wrote:The events I'd be interested would be typical: anyone approaching the car you see on the picture. I wouldn't mind falsies like motion around the other car on the right, or headlights reflection from other cars passing by or things like that.
anyone approaching the car :
people are not going to disrupt the bottom section of the image, their feet are likely to be around 10% from the bottom of the image with their head around half-way up. This is basically the region covering the main tarmac'd area up to the number plate of the car. I would set up 3 regions (in line with the parking bays) at this range. If you feel that someone might approach the car by sneaking along the back wall, then you will need an extra (3) region that covers that as well. Since the posts are likely to reflect headlights of other cars, give each of these their own region. If your car is moved, then its primary motion will be FORWARD, and as such it won't alter the image too much, give the car it's own region and be prepared NEVER to get the settings for it right!
As you will have guessed, *my* approach would be to divide your image into Loads of regions (at least 9), and set them ALL to active with the highest sensitivity setting that a zone has by default. This will generate LOADS of events (90-99% false), but then you'll be able to see what the TRUE events do to each of your regions. You'll also be able to identify zones that only trigger when there is a FALSE event (and you can therefore set to preclusive).