I have had a CanoScan FS4000US for several years.  It does great scans
at 1k, 2k, and 4k ppi.  It also has the infrared "spot removal" system,
which Canon calls FARE.  It scans strips of up to six 35mm frames or
slides.  The problem is that it's slow.  I mean dead dog slow.  At 4k
ppi with FARE enabled, scanning an entire "rack" of six takes a /looong/
time.  It's been a while since I scanned any film, but IIRC it was like
15 minutes or more for six scans.  Might've been longer.

Something to be aware of is chroma noise or grain aliasing.  At
resolutions around 4k ppi with many films, the physical size of a
sensor's view on the film and the grains/clouds in the film base are
getting (relatively) close to the same.

That causes some sampling problems (vaguely related to moire) that lead
to colored speckles in the image.  It's like noise in a B&W photo, but a
rainbow of colors.  At 2k ppi or 1k ppi, it doesn't show up.  At 3600
ppi it's starting to show up a little and at 4k ppi it can be bad,
depending on the film you're scanning and the photo in it.

There were several long discussions about it here on the PDML back
around 2002.  One, in particular, I started on 26 March 2002.  I wonder
if there are any archives that go back that far.  If not, maybe I'll see
what the PDML can collectively check their local archives for those
discussions.

-- 
Thanks,
DougF (KG4LMZ)

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