Can anyone tell me the real differences between render layer attributes and associated passes? for example, getting a depth map or AO render seems possible using both methods.. but what's the real difference between the two?
I realise it's all dependent on 'what you want' - I just want a simple way of getting a depth map. I can get a luminance layer set up, but it seems it'd be much easier to add a pass to the layer. Passes sound like the answer, though I can never get them to work. On top of these there's contribution maps, overides. And a Z depth checkbox in the renderable camera settings.... that doesn't seem to do anything either.

Every tutorial seems to go about things a different way, so it's difficult to know which advice to take to avoid making things more complicated than need be.

thanks