Several years ago, when I worked at the U.S. National Archives, we tried
this "piped light test" with a few motion picture film stocks. We did not find
that acetate stock will pipe light and polyester stock won't in all the
samples we tried. We concluded that maybe the photographic emulsion coated on the
base material had something to do with light transmission but never did any
organized testing with all kinds of emulsions (color, b/w, negative,
positive, mag stripe) on the two base types.
Alan Lewis
Washington, DC
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