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filmscanners: Workflow for web lens comparison

Hi all - 

I'm trying to do something that is really pushing the envelope of my
understanding of resolution optimization (a good thing!).

What I want to do is compare photographs taken with a 200mm lens with
and without a teleconverter to try and pinpoint some of the exact
degradation introduced by the TC, and post them on the web for a SI
discussion group I'm a member of.  .  We'll take it as a given that I
have two photographs of the same subject that are both perfectly in
focus (I thought I did, but I don't yet.)

The photograph in this case is of a chimney tower with a wire mesh
grate at the top.  I want to post 4 photographs:  1 each of the full
frame photographs, one without a TC and one with.  Then I want to crop
the same exact area of the wire mesh and part of the wall detail - a
quite small portion of the overall photograph - and then size them to
the same size onscreen,  so they can be compared.  

First off, I'm not entirely sure what settings to use in order to show
the full frame photos at their maximum resolution.  They were scanned
at 2720 dpi.  Resampling downgrades the quality a lot - so should I
resize simply by scaling?  PS Elements scaling dialogue seems to be
aimed primarily at print dimensions, i.e it's in inches, cm, picas,
columns etc.  Just divide the desired screen size in inches by the
pixels?    What's the best way to size the TIFF for screen while
maintaining max resolution?

I think I'm clearer on the detail crop - I can leave that at 2720 dpi,
and pixel-size it with a resample without losing much quality.
However, I'm not sure I'm correct about that.

Can anyone suggest any ideas for a workflow that maintains as
consistent an image quality as possible across all these different
sizings, and that stays as close as possible to what the lens/film
actually produced?  That would include some optimum Vuescan setting,
too I imagine.  This first round of experimenting was done on Portra
400VC, and I used the setting for that in Vuescan, with a "light"
grain reduction filter.  The colors came out fine.  

Thanks, I know I'm probably missing some basic concepts here, so
thanks for your patience.  

Ken Durling

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