Rather than using a silver based emulsion as the final emulsion or
film , you could use a glass coated with gelatin with a aniline dye (
aniline dyes are generally transparent) , sensitize the emulsion with
ammonium dichromate .. Aniline dyes I believe is what Kodak uses in many of
their gelatin filters.. The first image would be silver based fine grained
negative film but then you would contact print the gelatin dye coating to
create the filter.. In essence what you are doing is making a carbon print
of the light fall off.....
The big problem would be to determine which dye has the neutral density
characteristics...Creating a center filter in red, yellow , orange or green
filter would probably very easy information to come by as isochromatic
photography is based on the various dyes ability to absorb different parts
of the spectrum of light.., but I would not even know where to begin on
creating a neutral density dye...
Another problem would be to make the filter so the fall off is equal to that
of the lens when placed in front of it....
jc
> This is an idea that has been rattling around in my imagination for
some
> time also. I expect that it might work, with some important limitations:
> (1) Wouldn't the granularity of the filtering medium (developed silver
> grains) cause a loss of image quality, especially since the vital central
> rays are the ones which will be subject to the greatest filtration?
> (2) The ability of the filtering gradient to exactly balance the falloff
of
> the lens might be a problem, although perhaps not if you could manage to
> contain the filtering characteristic within the relatively linear portion
of
> the exposure vs. density curve.
> RKS
>
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