[rollei_list] Re: Old film

At 12:00 PM 5/30/2005, Richard K. wrote (in part):

>I don't know why Kodak has been trying to kill off Kodachrome but they 
>have for a long time. Probably supporting the special processing is the 
>problem. Kodachrome evidently has excellent dark storage properties while 
>Ektachrome type films have better resistance to fading under projection. 
>I've seen quite a lot of Kodachrome that still looks pristine after 60 years.

Richard, I don't know why either.  Nobody has come up with anything in E-6 
that has its characteristics.

>  I am not sure why the dyes are so stable. Kodachrome differs from more 
> recent color films in that the substances which form the dyes are in the 
> developing solutions rather than in the emulsion layers.

As I understand it . . . from what I've read about its invention and how it 
works as a color film . . . Kodachrome is actually a B/W film.  The 
difference between it and Ektachrome is the dye linkers . . . the chemical 
compounds that pluck the dyes out of the developing solutions into the 
appropriate layers.  Kodachrome doesn't have the dye linkers in its 
emulsion; Ektachrome does.  One of the Kodachrome developing steps (from 
what I've read) is apparently the introduction of the dye linkers . . . 
something that the Ektachromes (and all other E-6's) do not need as they're 
already present.  This gives Kodachrome one of its unique 
characteristics:  contrast edges that appear finer and are better defined 
for its granularity than the Ektachromes have giving it a greater apparent 
sharpness compared to Ektachrome of similar granularity.  Reason?  Without 
the dye linkers present when the film is exposed, the emulsion is thinner 
and oblique ray paths traverse less lateral distance through the emulsion 
during exposure.

>Kodachrome has a curious history. From bits of history gotten from various 
>sources it seems that George Eastman got interested in finding a practical 
>color film for amateur photographers.

 From what I read (and cannot find the source), the principles behind 
Kodachrome were created by two amateur photographers who had more time on 
their hands than they knew what to do with and were experimenting with 
methods to create color film.  They took what they had to Eastman, who 
didn't do anything with it.  It did (either approximately then or some time 
later) end up being presented in some manner to one of Eastman's research 
scientists or engineers . . . fairly high up in the organization (if not 
the top guy) . . . who saw immediately that it was a path toward a viable 
solution to the color problem . . . something Eastman Kodak was in a 
desperate race with Agfa to create and get to market before they did (which 
you discussed).  The two individuals may be the Mannes and Godowsky you 
referred to.  The basic problem everyone was working on was getting the 
correct dyes in developing linked to the correct grains that had responded 
to the color of light the dyes represented.

The original Kodachrome developing used colored light as you described, but 
as I understand it, this has changed (when I don't know) and the current 
method chemically fogs it instead of using light.

I make no claim about being 100% accurate in this . . . it's what I'm 
pulling from memory from a couple years ago after I got curious about what 
Kodachrome is and why it's so different, and started a quest of web 
searching for details.

-- John Lind

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