[Leica] More from the early 50s

[henningw at archiphoto.com (Henning Wulff)]

At 1:06 PM -0700 4/17/05, Frank Filippone wrote:
>It's the dyes.  They are permanent.  They do not exist in any E4 or E6 or
>C41 film.
>It is also important to properly store the slides.
>
>Frank Filippone
>red735i@earthlink.net
>
>Very nice! Does anyone know if a (C41 or E6) film exists today that
>would give the same colours?
>
>All the best from the south of France!
>
>Tarek
>

E-4 (precursor to E-6) films won't last as well, and many are 'gone' 
already. E-6 films, especially the ones made in the last 10 years and 
processed properly, might well be as fade resistant as Kodachrome.

The situation today is that E-6 films are longer lasting under 
projection, and that Kodachrome might still have the edge under dark 
storage. Check back in 50 years.

There are no 'permanent' dyes. One of the reasons why Kodachrome has 
been so much better is that the dyes, as complete dyes, are added 
during processing. The film as such does not contain the colours we 
see in the slide at all. The only colours in the film are the filters 
in the layers. Anyway, there is a much wider range of dyes and 
pigments available that are suitable for using during the development 
than the dyes in E-6 and E-4, E-3 etc. films that have to be created 
by chemical action during the development of the film. The components 
of those dyes have to be present in the film layers when you shoot 
your picture, and then become dyes during development, with the 
excess bleached away. This is more limiting as there are fewer dyes 
that can be created this way.

Now the knowledge and capability of film manufacturers has increased 
to such an extent that very stable dyes can be created this way. In 
the 50's and 60's this was not possible.

-- 
    *            Henning J. Wulff
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