[MF3D.FORUM:68] Re: Apparent image size, MF verus

["Bill Glickman" <bglick@xxxxxxxx>]

Rich

      Excellent piece.. thank you, it's always nice to know where things are
heading... I have not kept up to date on such...

Regards


> Bill -
>
> The speed increase (from what I have read in a news item from Photo
Marketing
> Association International - www.pmai.org) could be 10x (~3 stops).  This
is all
> still very much in the research stage.  One potential problem to be ironed
out
> is how the formate will affect spectral sensitivity (i.e., will it react
with
> the sensitizing dyes used to make a film panchromatic, or sensitive to a
> particular color range).  I wouldn't wait too long to buy a new lens -
this
> research may take a while.  By the way, Kodak has also been researching
> chemicals that do what formate does, but they haven't announced any
related
> commercial products.
>
> Exposure latitude is a function of film contrast, not sensitivity.  It has
> usually been the case that faster films have had more latitude, but that
is a
> consequence of their having lower contrast.  Most of a film's contrast
> characteristics relate to the distribution of grain sizes.  The more
uniform the
> grain size, the higher the contrast (i.e., grains of the same size tend to
> 'switch on' at the same light level).
>
> Lithographic films have extremely high contrast, extremely fine grain, and
a
> very narrow range of grain sizes.  It takes special compensating
developers to
> eke out a gray scale from these films (when a relatively small number of
grains
> in a given area are reduced to metallic silver, the local development
> environment is changed by exhaustion of a very dilute developing agent
and/or
> release of by-products to inhibit the development of nearby grains just on
the
> threshold of changing to metallic).
>
> High speed films undergo a longer AgX crystal growth stage to produce
larger,
> more sensitive crystals.  But growth rate is not uniform, so you tend to
get a
> broader range of crystal sizes - an lower contrast as a result.  If this
new
> 'formate' process increases sensitivity without extended crystal growth
(and
> grain size distribution), special measures might be needed to tame the
contrast
> (the 'chrome latitude situation will probably not improve).  On the other
hand,
> current high-speed, moderate contrast films could become "ultra-speed",
moderate
> contrast films without grain increase or loss of exposure latitude.
>
> Rich
>
>