I have FluidMask3 - great program. When I bring in TIFs of dogs that need to be cut out (against white), I then save as PNG and bring into PS for compositing.

When I bring them in they are noticeably lighter than the original TIFs and I have no idea why. Same thing you're talking about - colors are more muted, the blacks are decidedly NOT black.

Solution?

Bring the PNG AND the original TIF (in YOUR case, render a TIF version) into the comp, Line them up (I put the PNG on top of the TIF layer and change the mode to Difference - use the Move Tool and your keyboard's Arrow keys to line them up - how you'll know they're perfectly lined up is it will become perfectly black - meaning there is no "difference"), then Ctrl-click (Cmd-click for Mac) on the thumbnail of the PNG layer to Load the Selection, then Ctrl-j the TIF Layer to duplicate ONLY the exact same pixels of the PNG Layer.

Did that make sense?

Hope this helps - good luck!

-Lew