I knew about fb paper, but not film. Are any current B&W films even coated on Estar? I'm surprised about the film changing size. If this is true, how is it that masking works? Wouldn't the mask be out of register once processed?
All masking and matrix film was made on Estar. It was done to prevent registration problems.
All paper materials shrink or expand depending on length vs width (warp vs woof! ).