Did not see the question for me : So sorry for the delay

We coat miniature and roll film on tri-acetate, sheet film on polyester :

We would never coat miniature or roll on polyester, due to the hightened
possibility of camera damage, polyester does not tear and therefore in our
opinion is not suitable for a camera film base, so we do not use it.

POLYESTER is OK for lots of other miniature applications such as aerial / surveillance
etc. etc. and its thinner so it has other advantages in certain applications

Regards Simon ILFORD Photo / HARMAN technology Limited :