From: Jeffrey D. Mathias (jeffrey.d.mathias@worldnet.att.net)
Date: 08/04/00-05:22:55 PM Z
Carl Weese wrote:
> ... Not sure if this applies to Jeffrey's 'behind the scenes' idea, but
> small format enlargements benefit in mysterious ways from differences in
> the appearance of film grain. Most obvious is that a picture that isn't
> sharp may look sharp if the eye has a corner-to-corner grain pattern to
> anchor on while looking at the soft image.
This is true. However, what I have observed is different in that the
presence of grain in the negative seems to improve the discrimination of
tones in a Pt/Pd print. So in addition to the apparent sharpness as
Carl mentions, there is an actual sharpness resulting from an effect the
grain provides. The reason for this effect is not known at this time,
but is suspected to be related to edge effects, gradients of the modular
transfer function, and such to keep the optical mathematicians busy.
Note that I do not know if this effect works for other printing
processes, or just Pt/PD, or just certain processes, or all the time.
Judy Seigel wrote:
> ... If he (or anyone) would explain that in
> simple terms (like for August), would be appreciated.
In simple terms, I don't know why, but I can show you the observations.
The experiment is as follows:
+ Photograph the same scene with two (or more) films (and certain
developer combination) having different grain characteristics.
+ Make Pt/Pd prints.
+ Evaluate.
I have scanned negatives (made in 1986 when I first observed this) and
Pt/Pd prints (made today from the negatives). The prints were made
using Strathmore 500 Artist paper, vintage 1987 (their old process)
because this paper renders detail better than other papers I have. This
data can be found at the following link:
http://home.att.net/~jeffrey.d.mathias/info/grain_effect.html
Observation with a magnifier is better than the 1200 ppi scans, but the
scans still demonstrate this grain effect.
-- Jeffrey D. Mathias http://home.att.net/~jeffrey.d.mathias/
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