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Old January 24th 04, 09:55 PM
HypoBob
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Default Anti-UV layer in films???

Jean-David Beyer wrote:

HypoBob wrote:
A couple of years ago I read an article about UV photography and
learned that one problem that UV photographers have is that most
color films have a UV blocking layer that keeps UV away from the
emulsion.

Does anyone know if any black and white films, particularly the newer
T-grain versions, have built-in UV blockage?

I do not know, but I very much doubt it, since there is no particular
need for it. The shorter ultra-violet would be blocked by the glass in
the lenses. The problem with the blue and ultra-violet in color films
is mainly that you do not want them to excite the green and red
sensitive layers, so they put a yellow filter between the
blue-sensitive (top) layer and the others. It is probably mainly
colloidal silver that would be removed in a bleach or fixing step.

I suppose there could be an ultra-violet blocking layer over the top
of the film; I guess this could reduce the apparent sensitivity of the
top layer. The books I have read do not mention that, but the most up
to date one I have is from about 1966 (Theory of the Photographic
Process, Third Edition), and they may have changed since then.

For B&W, anyone who needed it could use a weak (or stronger, of
course) yellow filter such as a #6.

Jean-David,

One thing that triggered this question is that the Kodak TMax films are
said to have a "reduced blue sensitivity", to the point that some say
the unfiltered films perform as if there were a weak yellow filter on
the lens. It seems that an easy way for Kodak to achieve this effect
would be to transfer an already 'tried and true' technology from their
color lines to the TMax line.

If Kodak is blocking UV for us at the film plane, then that UV filter is
one less piece of glass that needs to be between the subject and the
film in critical applications.

Bob