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From: hagerman@nermal.DEC
Newsgroups: net.rec.photo
Subject: film sharpness
Message-ID: <2807@decwrl.UUCP>
Date: Thu, 20-Jun-85 23:35:37 EDT
Article-I.D.: decwrl.2807
Posted: Thu Jun 20 23:35:37 1985
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x

Someone was wondering whether Kodachrome was really all that much
more fine-grained than the other available color films.  I went
down to the local camera store and looked in a Kodak book called
the Professional Dataguide (I'm too cheap to buy one), which
lists film data for all of Kodaks color and black and white films.

They break resolution (lines per milimeter) and graininess into
groups and give the results by group, such as high, very high, etc.
Without memorizing all the data, in the group with high resolution
and extremely fine grain were Kodachrome 25 and 64, Kodacolor II
(ASA 100: it must have been an edition from before the new color films),
and Plus-X.  Not included were any Ektachrome films.

This kind of goes along with what you'd expect from technological
and marketplace considerations:

1.  Reversal films such as Ektachrome are inherently finer grained
than the equivalent negative film, because in the negative film
the image is made up of the larger grains of silver which pick
up light better.   In a reversal film, the image is made up of what's
left after the large grains are removed in the reversal process, i.e.
the smaller grains.

2.  But market conditions are that most pictures are made with
color negative film, therefore they put more effort into the negative
films.  An example is the new range of high performance print films.

3.  Kodachrome has an advantage over Ektachrome because the emulsion
is thinner.  This is because the dye is added in during processing in
the Kodachrome method.

4.  Black and white film has the advantage of a very thin emulsion
and no color filtering needed, so is finer grained for a 
given film speed.

In regards to Mike Rosenlof's ranking of sharpness problems,  anybody
who has ever seen an 8x10 contact print knows that graininess is
a big factor.  One reason auto-focus cameras are
so successful is because for the first time, the average snap-shooter
now gets back prints that are in focus.  Camera shake is a problem
if you can get things focussed right.  But back to reality, aren't the
full-page spreads in Time, Sports Illustrated, etc, good enough?
They're mostly taken with 35mm film, hand-held...

Doug Hagerman