>I don't think ProviaF uses dyes that are IR opaque, no matter how
>dense... In fact, try a piece which is totally unexposed (like from the
>camera leader) and see if that is at all opaque to IR. I doubt it.
An often-raised thread on the various Infrared Photography lists concerns
using one or two layers of unexposed, processed, E-6 film as an IR filter
for flashes or sometimes even behind the lens. Several posters have
indicated that it works pretty well, but is not as good as a filter
designed for the purpose. That would indicate that unexposed, processed,
E-6 is relatively transparent to IR even though it may be almost opaque to
visible light. Might this vary from one E-6 film to another? Probably, but
I would guess only in degree, not in kind. That is, I would expect all E-6
film to be relatively transparent to IR.
Photography by Stan McQueen: http://www.smcqueen.com