Hi -
Okay, so I had a conversation with one of our Senior Graphics Architects to make sure I understand exact what the Opacity Node is supposed to yield. While we can argue that the naming of Opacity is misleading, it actually refers to the opacity needed to help render subsurface opaque materials and this is the main reason that this buffer exists. So in terms of a 0…1 range, an Opaque material that has No Opacity would render as a 1 and with full opacity would be a 0 which is the behavior that I am seeing in 4.8.1.
Thank You
Eric Ketchum