This is what the jpeg sequence video look like after rendering. The fog is not stable.
[video] http://youtu.be/Mo4nrE41H5Q[/video]
Here is my compositing node setting
I’am using the official blender 2.73 win 64
Do not use the normalize node with animations, it will scale everything to compensate for changes in the max Z value. Use math or map-value nodes instead.