Re: Generation of slides

[P3D Greg Marshall <greg.marshall@xxxxxxxxxxxxxxx>]

Sid Herbage  writes:
>>> Come on! RE-EXPOSED? To what? Not light! Because there's an extra bath
it's
>>> second generation? Developer, reversal, color developer... there is no
>>> second generation-
>
>>I had always understood that in a reversal process, (maybe not ALL
>>reversal processes?) there was indeed an exposure to light, partway
>>through the development process.
>
>Years ago, when I used to process my own slide film, the re-exposure
>was done using light for all manufacturers processes as I recall. However,
>this wasn't particularly convenient in a commercial processing setup and
>the chemical fog bath was introduced.
>
>I haven't done such processing for a long while now, so I've no idea how
>amateur processing currently does it.

It used to be true that reversal processes involved exposure to light,
but
generally not any more - the same effect is achieved chemically.

All of which has nothing to do with whether a processed slide is a first
or
second generation.  One could argue (I tried once and failed) that the
dyes in a transparency constitute a secondary image while the original
emulsion is removed.  The problem with this argument is that this
happens at almost the molecular level and certainly doesn't involve any 
optics, so there is nothing like the generational loss that happens in
steps such as making a print from an original.

On the other hand, I won the argument that negative color film generally
is sharper than transparency film.  People get this confused because
we all know that a print is not as sharp as a slide (well...), and how
else would you use a negative but to make a print?  Well I'm a digital
photographer and scan both negatives and positives.  For other reasons
I prefer and mostly use transparency films, but for ultimate accutance
and resolution, negative color film is the clear choice.

Greg Marshall


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