These are processing bit depths - they have no impact on your source material, so you can change infinitely between the two modes without any loss.
thanks for your reply.
I'm aware that it won't affect my source material. What I really mean is - imagine a project with lots of keylight stuff going on and different alpha-mattes or luma-mattes with manual painting in the mattes to fine-tune the mattes coming from a 3d-app. So - when I switch to 8 bpc now - and back to 16 bpc again: does all my details in the mattes, keys, and so on will stay the same?
Sorry for my english...maybe my question is not perfectly clear?!?
Switching the project setting from 16bpc to 8bpc to 16bpc loses nothing.
Alright...thanks to everyone involved!