How to get less sensitive to fluctuations of brightness

Question

Hello,

I set up motion to capture a video if there is a motion within image of my door cam - that works great. The main part of the image consists of the wall and the door of the house. I created a mask only analyzing these parts because the should never change and a person who want enter the house has to go there. Unfortunately there is a street next to the door/wall so that every times when a truck drives by the wall and the door become a bit darker and motion starts recording. My question: Which parameter do I have to change so that motion will detect a person passing by but not the change of the brightness of the whole mask area (not a fast but a slow change).

Environment

Motion version:	3.2.12
ffmpeg version:
Libraries:	ffmpeg, mysql, postgresql
Server OS:	Debian Wheezy 7.5

-- RoBra81 - 17 Oct 2014

Answer