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filmscanners: Nikon Coolscan IV Focus



I have posted on the list a couple of times that I find no lack of depth of
field on the Nikon Coolscan IV - LS-40.  After seeing several posts that
question the depth of field on the LS-4000, I decided to perform an
experiment with the Coolscan IV and post the results found here:

http://www.photo.net/photodb/folder?folder_id=117469

This is a comparison of the corner portion of a Kodachrome slide scanned
using three separate focus points on my Coolscan IV using Nikon Scan 3.0
with the Digital ICE "off".  I selected an old slide of no particular
artistic value.  The slide shows about average curvature in the mount for
Kodachrome.

The first image shows the corner section with the autofocus point at the
center default.  The second image shows the results moving the autofocus
point to the lower center of the edge.  The third image shows the autofocus
point dead on the flower pedal in the corner enlarged.  The whole slide scan
is shown as the fourth image with the corner enlarged highlighted. The
values of the manual focus slider in the tool pallet of Nikon Scan 3.0 were
101, 99 and 96 respectively.

I saw no difference in the quality of the focus with the raw scan data
imported into Photoshop 6.0 scaled to 300%.  Any larger scaling  of the
images showed pixels.  The JPEGs posted show what I saw at a 300% scaling of
the raw image.  The LS-4000 may have different optics or the greater ppi of
the LS-400 may show more critical focus but the 2900 ppi of the Coolscan IV
does not show any focus problems to me.

Douglas F. Landrum
Laguna Beach, California
dflandrum@earthlink.net




 




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