Quote Originally Posted by Prest_400 View Post
Polyester seems to have some interesting advantages, and it's drawbacks don't seem that important on still cameras. I'm curious on how it doesn't seem to have replaced Tri-Acetate on the still film market; obviating maybe 135 with motor winder use.

The last couple of years worth of EFKE production were on Polyester, as are all the Maco films derived from industrial film made by Agfa Belgium. The main problem is light piping. Motion picture Print stock has been on Poly for years, the esta strenth is needed for the Plater drive systems where an entire feature 12,000 ft is stored on one roll

Quote Originally Posted by Prest_400 View Post
What would happen if the same thickness and material between the three kinds of finish (135, 120 and sheet) were used? I guess it would be an issue for roll film cameras when it comes down to winding tolerances. But it would maybe make lower scale manufacturing easier (one master roll for everything).
The movie print stock was made thinner than the acetate to give it about the same stiffness so that the film would run comfortably on existing projectors. in this application the thickness of the film does not matter to foucs as the emulsion is generally facing the machined fixed part of the gate on the lamp-house side. Sheetfilm is made these days in thick poly as it is stiffer than acetate and stiff is needed to hold Flat. Sheet film thickness would be too hard for roll film cameras to deal with. even film as think as the Poly Movie print might be a bit stiff.