> Anyway, I think that the original point was that unless one takes
> special
> care to avoid vibrations and to focus carefully, a 4000 dpi scanner is
> overkill, and a 2880 dpi unit is adequate or better.
That is what I disagree with. It's simply not correct that 4000ppi is a
waste of time unless you use a tripod/mirror lockup/shoot on slow sharp
film/ use optimal lens apertures. Inadequate resolution is as destructive
of whatever quality the original has as a poor enlarger lens, though
whether it matters is another question which depends on intended use.
Back to back tests I've done show that 4000ppi gets more off the film,
though I would not characterise this an enhanced sharpness so much as the
sort of qualitative gain in tonality and inner detail that you see in a
comparison between slow and medium speed film, eg PanF vs FP4. The slower
film is a little sharper and quite a bit smoother, and 4000/~2700ppi have
a similar equivalence.
Whether this matters depends entirely on your priorities and intended use.
In an A4 Epson print, there is a difference which makes the lower res
units look very slightly diffuse, as if there's a trace of Vaseline on the
lens. This is a low-order effect which would seldom be noticed except in a
critical side-by-side comparison. However, it's quite clear, even in a
hand-held shot. To keep this in perspective though, I don't feel any need
to re-scan images I've scanned at 2700ppi.
There is no reason to think 4000ppi is a magic number, either. I've seen
comparative scans at 4000, 8000 and 120000ppi. Although diminishing
returns set in firmly around 8000ppi, the 12000ppi scan still shows some
marginal improvement. If you look closely this is largely confined to
accurate rendition of grain shapes but still enhances the overall acutance
and tonal quality.
Regards
Tony Sleep
http://www.halftone.co.uk - Online portfolio & exhibit; + film scanner
info & comparisons
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