My impression (correct me if I am wrong) is that
there were two types of film. One was the original
reversal film such as Zapruder originally shot.
Then there is a special copy film used only to make
copies. I think the copy film only needed a standard
one-step developing, which Jamieson could have done.
But Zapruder's partner Irwin Schwartz said in the
MPI interview that after the 3 copies were made
at Jamieson that they had to take them back to
Kodak to be developed. I seem to remember that
Jamieson had run out of regular 8 mm copy film
and had to use 3 reversal films just like Zapruder's
original to make the copies, but they did not
have the setup to develop reversal film there, so
Zapruder had to take them back to Kodak to be developed.