Since
film has a black anti-halation base coating,
light has a tough time passing through this
layer. This is why the emulsion always faces
the lens of a camera - this original footage
is a B-wind and reads correctly through the
base. The term "read" refers to its
orientation. Suppose a billboard was shot on
film with the emulsion properly facing the lens.
After processing, the words would read backwards
if looking at the emulsion side of the film.
Flip the film over to the transparent base side
and the words will read the way they are supposed
to. This is why B-wind film reads through the
base.
