From: Jeffrey D. Mathias (jeffrey.d.mathias@worldnet.att.net)
Date: 05/21/01-06:09:34 AM Z
Darryl Baird wrote:
> ...
> ... knowing what resolution is needed to
> exceed the size of film grain. If your resolution is sufficient to make
> marks on the film which will not be seen as anything but film grain, you
> have enough resolution. ...
> In short, full resolution isn't what the scanner can produce, but
> what you need to replicate film grain size. ...
I would add that especially when considering alternative processes,
consideration must be made for the actual alt-photo printing materials
capabilities to deliver (or respond to) a certain resolution. The full
resolution required might likely be less than that needed to replicate
film grain size.
One of the most resolution limiting materials can be the paper used for
the print. A paper with a rough surface texture can deliver far less
resolution than a paper with smooth surface texture. An example for
determining the resolution ability of a paper and materials for a
particular process (in this case Pt/Pd) can be found in Chapter 13 of my
guide, section titled "Appendices to Building Digital Negatives",
"Resolution".
(Web site link at end of this post.)
This includes scans of actual Pt/Pd prints as demonstration. Note that
the Crane's Cover-90 paper with the Pt/Pd process is capable of and
should seem to
require a resolution of about 600 lpi. This could differ for other
papers
and other processes.
An interesting application of this knowledge could be to use a rough
surface paper so as to not require as much resolution from the original
scan or digital negative.
Another consideration, especially for very large prints, is that one
should consider from what distance a viewer is likely to look at the
very large print. A lower resolution at such a viewing distance may be
as much information as the eye can handle
anyway. Although consideration should include that negative resolution
may impact more than just print resolution (such as tonal discrimination
or posterization).
Still another consideration is the relationship of grain size in the
negative and detail in the final print. In my guide, the study titled
"A Look at Grain in the Film and Details in the Print" (in Chapter 15)
demonstrates how a finer grain can result in less print detail. I have
not seen any other information on the results in a Pt/Pd print as
related to negative grain size and/or shape. This may be a valuable
study when considering what resolution may be optimal for digital
negatives used to produce Pt/Pd prints.
-- Jeffrey D. Mathias http://home.att.net/~jeffrey.d.mathias/
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