Wow. Just tried your setup with the Forward rendering path and indeed, it breaks in a crazy way. I found what's causing it : Unity's [ImageEffectOpaque] attribute. This is definitely a bug (also in Unity 4 !) and it should be reported. It breaks SSAO effects, Global Fog, etc. If you go into SSAOPro.cs and comment line 257 (assuming you're working with an up to date version) you'll find out that it fixes the issue your getting... But it will cause SSAO to be "see through" on transparent objects. So unfortunately, I'm not sure if there's a good workaround for this bug, aside from switching to a deferred rendering path. A potential solution would be to render your cameras in a render texture and blit it on screen but it can be messy to set up... Edit: tested on Unity 4.6 and 5.0.1, 5.1.