ok 2 things... 1 Final Gather just quit working. second I have made some trees with leaves on a plane with transparency's. I have a sky dome that should be working with FG. when the leaves are against the sky you can see a different shade of blue from the sky where the transparency should be. lookin like glass with some refraction but refraction isn't on at all. FG isn't working but I still get the blue artifact against the sky even though it's not lit up. I just went through a post that added the mib_shadowtransparency to the shadow shadow which made the shadows on the ground nice and pretty but I still get this glass effect on the transparency against the sky dome. and it doesn't do it when looking at the leaves against the ground. must be something to do with the incandesence of the dome. maybe I have to map an alpha to the incandesence of the dome. I don't know I'm goin nuts here spent all day yesterday playing with this one part.
I had the same problem with some trees (that were originally Paint Effects) and Final Gathering. The trees were fine over geometry but showed the blue on black. What I did notice is that once I composited the scene with the blue sky, the effect of the blue on the leaves was not noticeable. I imagine what we are seeing is the reflection not the transparency of the dome. In any case I wasn't able to solve it for a render on black. Anyone?