Film base: Difference between revisions

==How to tell the difference between polyester and acetate==

* [https://www.nps.gov/museum/coldstorage/pdf/2.3.1b.pdf Here is a guide] for making a film viewer for easy identification of acetate or polyester film base. Older polarized 3D glasses (they use spherical polarization) work great for this if you can find some. Real-D glasses do NOT work. Polyester base will create a sort of "rainbow" effect when viewed between the cross polarized lenses, acetate base will not.

*You can also differentiate between the two by holding up the reel of film to a strong light. With polyester base prints the light will shine through, with acetate it will appear opaque. I find this is true most of the time though with certain film stocks it will be much less obvious than the photo example to the right. The polarized lens test is more definitive.

*Polyester is very difficult to tear with your hands, it stretches rather than snaps. Obviously this test is not recommended as it requires you to damage the film, though an accidental film break, or a tearing of the [[leader]] or countdown (if there is any) may give you an answer. Just make sure the leader is original to the print, as sometimes a leader or countdown may be spliced onto a print of a different base.

*A poly print may have "Estar" written along the edge of the print, acetate may have "safety". Although some new prints struck from acetate negatives may still have "safety" written on them. So it's helpful thing to check for, but use it along with other identifying qualities.