Archived posting to the Leica Users Group, 2001/07/26
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Go and look for your self.
http://www.users.qwest.net/~rnclark/scandetail.htm
Meino de Graaf
"Mxsmanic"
<mxsmanic@hotmail.com> To: <leica-users@mejac.palo-alto.ca.us>
Sent by: cc:
owner-leica-users@mejac.palo- Subject: Re: [Leica] Nyquist again (was scanning)
alto.ca.us
07/26/01 12:32 AM
Please respond to leica-users
Johnny Deadman writes:
> In the case in question, as Austin points out,
> it is perfectly possible to position the sensors
> so you get a uniform gray.
Easier said than done. The sensors would have to be positioned with
perfect
precision, which would require a very contrived test, unlike anything that
happens in the real world. It would be equivalent to sampling a sine wave
at
precisely the points where it crosses zero. And the sampling frequency
must be
_identical_ to the target frequency, otherwise a uniform gray will not be
the
result.
All this has drifted quite a bit from the original point, though, which was
that
53 lp/mm is entirely adequate for most 35mm photographs (which rarely get
beyond
40 lp/mm), and that it is also quite achievable with a 2700-dpi scanner.
So
drum scanning at 16000 dpi will generally buy virtually nothing in terms of
increased image quality. A 4000-dpi scan results in a very modest
improvement,
and any more beyond that doesn't really change anything at all.