I am wondering if changing the internal ND's changes the back focus? For example switch from clear to one of the others does it change, or does it remain constant? I want to use it with a wide angle anamorphic which is very sensitive to back focus and want to make sure that I won't have to adjust the back focus every time I change the ND wheel. Specifically I would like to know for the F3 but other cameras would be useful too. Thanks in advance.
