on black, fog looks more like depth sorting the lower number starts at the camera and the higher number goes to the horizon. ..in order for fog to look like fog it must be the same color as the background..play with the color and you will see....and lastly is there any depth in your particles? it looks flat to me
Reading your response I realised that my expectation for the further particulares to became foggy (blurred) doesn't make much sense on a depth map. They should became darker, and that doesn't happen either.
The particles look flat because there is no depth in CC Particle World, thats why I'm building this Depth Map to be called by the effect Lens Camera Blur. I already cranked up the Fog value a lot to see if anything happens with no luck. I'm guessing this is a bug but I never saw this parameter being used so I'm not sure if it's me or a bug.
By the way, the particles are static and spread on all three axis. Could this be the problem?
if fog really is not working for you...wait...let me check something............Your gonna slap yourself...Fog does not work for lens convex, concave, or a few other presets...make the particle a textured disc linked to a smaller precomped whited solid layer and problem solved