plustek: A3I scan quality issues
Subject:
Re: A3I scan quality issues
From:
Gene Heskett ####@####.####
Date:
24 Sep 2002 05:06:26 -0000
Message-Id: <200209240101.52464.gene_heskett@iolinc.net>
On Tuesday 24 September 2002 00:26, Derrick J Brashear wrote:
>On Mon, 23 Sep 2002, Derrick J Brashear wrote:
>> I'm not sure I have the expertise to do anything useful, but I'm
>> willing to try working at it. Anyone have hints as to what the
>> problem might be?
>
>http://www.dementia.org/~shadow/out.jpg
>
>it was blown up by xv to illustrate the point
>
>the solid red background is true; the rainbow effect on the map
> scale is presumably pointing at some color channel error, an
> offset, because the scale is solid black, not color at all.
>
>I'm reading source now, but if anyone has a hint as to where to
> start, that would be helpful.
>
>Right now I'm looking through p48xx.c
>
>-D
This looks as if the scanner is "out of focus", which to a scanner,
(at least to my Epson 1250u) is equal to being out of registration.
My problem with that statement is that since the scanner is a
vertical motion device, the miss-registration is normally displayed
in an up and down manner, not the left-right error we are seeing.
Was this clip rotated 90 degrees maybe?
This looks to be a fairly low res scan, 300 dpi or so, what would it
look like at the scanners full resolution capability? This could
be even more illuminating, if only to add to the puzzlement I have
now. Since those maps are in all probability a half-tone process,
we would need an image that exceeds the size of the halftone dots
in working resolution, say 1200 or more dpi, more being better in
this case. What I can see looks as if they about matched, and this
is guaranteed to generate a moire pattern between the dots and the
scanners working pixel size. That can get downright ugly results
at times.
Registration, or focus is normally a function of the drivers
compiled in data sources and would be adjustable with a re-compile
after making the change in that variables value. Someone with
intimate knowledge of that drivers setup would be needed unless the
sources are well commented. The variable controls how close to the
image plane the actual scanner tractor and its imager is as it
travels down the page.
--
Cheers, Gene
AMD K6-III@500mhz 320M
Athlon1600XP@1400mhz 512M
99.16% setiathome rank, not too shabby for a WV hillbilly
