Hi, I'm trying to render some particles with low opacity (0.2) and I want the position pass (Pz). Rendering it out with his default setting gives me a wrong value (exactly his value / his opacity, so if the real distance is 10 the value will be 50) so I changed those values:
Sample Filter: Closest Surface
Pixel Filter: minmax min
I “feel” that this way it work .. but I'm not sure. Is it supposed to works this way? And both if is it the right or the wrong way … why? How it works?

Thanks!
Marco