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[filmscanners] RE: over resolving scans



Anthony,

>At certain key scanning resolutions, which vary by film, exposure, etc.,
>there is some interaction between the scan and the grain in the image that
>may create the impression of larger or more obvious grain in the scan than
>is actually present in the film.  If the resolution is held below this key
>threshold, grain simply blurs out of existence (but detail does, too); if
>the resolution is raised above this threshold, the interaction disappears
>and grain starts to look as it would on an optical enlargement.

Essentially, I agree with you.  The key point is where those key resolutions
lie for any given film. exposure, development process, etc.  I think you
will agree.  Consequently, it does make any generalized statement such as
found in the original post most difficult to confirm or deny or to offer
specific reactions to since no mention was made other than of Tri-x as the
film of exposures, development, etc.  I think that the particular key
resolution would also be dependent on the particualr scanner being used, its
design, performance characteristics, and the like; thus that key resolution
could vary quite a bit from scanner and scanner setup to scanner setup.
This, in part, is why I said that increased resolutions might have the
drawback of producing more apparent and obvious grain or alaising artifacts;
I also said this based in part on several posts that I have seen which
complained about grain and alaising being a problem at higher resolution
scans ( some based on films other than Tri-X but some based on it).  I
personally have not found this to be the case, at least that I noticed, in
my personal experience with the silver halide b/w films that I use.

Obviously, I think that complaints about alaising and grain resolution at
any scanning resolution are often based on matters of taste and preference
as to what is considered a problem.  Some prefer the blurred appearance of
the silver halide grain structure even with the lose of detail over a clear
well defined appearance be it the overemphasized impression found at the key
resolution or that equivalant to what they would see or get on an optical
enlargement  (I think this is the case in part because many people today are
accustomed to seeing dye based color films and now b/w films and do not know
what the grain structure of silver halide film looks like on the film - let
alone what it looks like on fast films like Tri-x).  It is for this reason
that I suggested in my original reply to the initial post that an increase
in scanner resolution *MIGHT* result in a limitation in terms of a greater
definition of grain and grain structure or alaising, leaving it up to the
user to decide for themselves if this is or is not the case for them.

At any rate, your comments clarified things in that they are not really all
that different from what I was suggesting, although from your original
statement of them I was not sure if that was the case or not.

>I actually prefer no grain at all

I gathered that from your comments, which in part was the reason why I
suggested that you might prefer the mushier depiction of the grain over a
highly defined depiction as being the reason you might prefer the lower scan
resolution; but right or wrong in this statement as to your preferences, the
main point of the comment was merely to emphasize the the evaluation and
decision was really in the end a matter of tastes and preferences.  "One
man's ceiling is another man's floor" sort of situation.  My comments were
not intended to be some sort of cryptic derrogatory evaluation of anyone's
(or your) tastes and preferences; and I certainly hope they were not taken
as being that by you or anyone else.

>Also, interestingly, Portra 400BW and some other chromogenic
>B&W films have incredibly fine grain, especially given their high speed

Technically, I do not think that the chromogenic B/W films have a grain
structure per se.  I believe that they like the color films have dye clouds
in contrast to silver halide grain, which may be why they sometimes are
easier to scan.  Even, if I remember correctly, Tech Pan's grain structure
is as well as its density range is very dependent on the developer that one
uses.  Use of traditional developers like D-76 will produce a grainier
result with less density range than one of the Technical Pan developers (
and even here there is a difference between the liguid and powder versions
of the Tech Pan developer, if I remember correctly).

-----Original Message-----
From: filmscanners_owner@halftone.co.uk
[mailto:filmscanners_owner@halftone.co.uk]On Behalf Of Anthony Atkielski
Sent: Tuesday, October 08, 2002 4:05 PM
To: laurie@advancenet.net
Subject: [filmscanners] Re: over resolving scans


Laurie writes:

> I am not sure if I understand fully Anthony's
> comments on grain or alaising on true silver
> halide films being emphasized and more noticable
> with lower resolution scans than higher resolution
> scans.

At certain key scanning resolutions, which vary by film, exposure, etc.,
there is some interaction between the scan and the grain in the image that
may create the impression of larger or more obvious grain in the scan than
is actually present in the film.  If the resolution is held below this key
threshold, grain simply blurs out of existence (but detail does, too); if
the resolution is raised above this threshold, the interaction disappears
and grain starts to look as it would on an optical enlargement.

This seems to happen a little bit with Tri-X at 2700 dpi, although it's
really hard to tell.  It is rumored that this happens with Provia and Velvia
at much higher resolutions, which may be one reason why they seem to show
more grain in scans than they actually have in real life, but I've not been
able to isolate clear evidence of this myself.

> He may prefer the mushier grain appearace to
> the sharper more emphasized one; whereas others
> do not.

I actually prefer no grain at all, but few films have such fine grain that
it cannot be detected even in the highest-resolution scans.  Tech Pan is in
this category.  Also, interestingly, Portra 400BW and some other chromogenic
B&W films have incredibly fine grain, especially given their high speed;
400BW has grain that looks a lot like Tech Pan, at least at 4000 dpi or
below (that is, it appears to have practically no grain at all).  This has
persuaded me to shoot a lot of 400BW; I don't like the way it reacts to
light, but the absence of grain is great, and allows cropping and
considerable enlargement.  For a good example of how well this film can
perform under good conditions, see

http://www.smallevents.com/portra400.jpg

Scanned on the LS-8000ED at 4000 dpi, with ICE set to normal, no GEM or ROC,
single simple, superfine mode off, monochrome 14-bit output, all other
settings at default.  I used Photoshop to pull extra detail out of a couple
of the deepest shadows and brightest highlights (the detail was present in
the scans but didn't really show on the monitor without pulling them a bit
towards the midtones), and to downsample in steps to 1600 pixels wide with
intermediate USMs of 98, 0.7 pixels, 2 threshold.  The focus point was on
the central figure in the image, the one with the vest.

I'm anxious to try Portra 400BW in 6x6; my mouth waters at what that might
look like!

> Personally, I always scan at the maximum optical
> resolution that the scanner is capable of ...

So do I.  However, since I happen to have two scanners, with different
maximum resolutions, I try to use the 2700-dpi scanner for films with so
much grain that the 4000-dpi of the other scanner isn't justified, just to
ease wear and tear on the latter.

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