Archived posting to the Leica Users Group, 2001/03/07

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Subject: RE: [Leica] Chicago Auto Show 2001 Photos
From: Richard Edwards <REdwards@Vetronix.com>
Date: Wed, 7 Mar 2001 14:43:30 -0800

The
> scanner, even at 2438 dpi,  seems to have a problem with the underexposed
> portions of the negative.  I have just downloaded Vuescan, but the first
scan
> done with it had the same problem.  I need to find out how to solve this
> problem.  Any suggestions?

Grain aliasing: http://www.photoscientia.co.uk/Grain.htm

Four solutions, in descending order of effectiveness:

1. Use a finer-grained film. All black-and-white films, in my
experience, get aliased by my LS2000, but with TMX or
Delta 100, you have to be looking for it at 30x enlargement
to notice the trivail aliasing. Obviously, slow film
is not a viable general solution.

2. Almost as effective as solution 1 -- scan at your scanner's
maximum DPI, then scale down the .tif file by a factor of 2 or 3
before editing or converting to jpeg. For me, this effectively solves
the aliasing problem, since the result is free of the nasty oatmeal
look, and the full 2000 DPI image is four times the size of what
you can see on a 17-inch monitor anyway. I am still surprised
at how well this eliminates aliasing. It works much better
than scanning at lower resolution to begin with.

3. Defocus the scanner -- easy in Vuescan. You
lose less detail than you would think. One reason for
grain aliasing is that the scanner lens is basically photographing
grain, which means it has too much time on its hands and
needs to get a life.

4. After scanning, using a filter in a photo editing
program: de-speckle and Gaussian blur seem
to work, but you'll be left to agonize over how
much detail you want to sacrifice to get rid
of the last visible trace of aliasing. In general,
filters are a software solution to a hardware
problem -- at the point the aliasing disappears,
so has much of the fine detail. De-focusing
the scanner is more effective and costs
less in image quality.

I've noticed that developers make a huge difference
here. Grain that is apparent -- but tastefully
understated :-) -- in your prints, may mean
ugly surprises when you scan the negatives.
D-76 seems a worse offender than even Rodinal -- I
can't explain this. After running APX100
in D-76 (both 1:1 and straight) and suffering terrible aliasing
problems, I tried XTOL 1:3 and aliasing ceased to be a problem --
sorry to introduce XTOL into every discussion, but this
seems to be one of its virtues. The answer may lie in 
how different developers shape the grain rather than
the grain size, since the XTOL 1:3 negatives don't
seem much less grainy than the D-76 negatives,
but the grain is less snappy.

Obviously, I have obsessed about this. I highly
recommend the link above -- it was my main resource
in solving this problem.

- -A L