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Re: Digital Scanners



Having read these comments and others with great interest, I'll pass
along my own impressions.  We have a Minolta PS3000, recently
installed as a virtually new machine.  This model will scan at a
maximum 400 dpi (also at 200 or 300 dpi), in three different modes:
B/W, something in between, and "Photo" (the latter certainly resembles
grayscale).  It will save images in one of three versions of
compressed TIFF.  Just a few weeks ago I completed a rather exhaustive
test, scanning samples of plain text pages, pages with intricate
engraved lines, and high and low contrast photographs.  I scanned each
example at all resolutions and settings, printed them on a 600 dpi
laser printer, and placed them in a binder beside the thing for future
reference.

Based on this test (which I do not claim to be scientific, although I
tried to limit variables and change only one at a time), the Photo
mode produces a very high quality photocopy image of a photograph, but
only at the 400 dpi setting.  I don't mean that the PS3000 will
produce a publishable facsimile, but it does do an excellent job of
producing a photocopy-quality image.  To test this perception, I also
copied the same photos on a high quality photocopier in our library,
that has a genuine grayscale photo mode.  While the photocopier
version was better than the PS3000 version, the latter was, in my
judgment, very good, and much better than I expected.  For intricate
line drawings or engravings, the 400 dpi photo mode also worked best.
For plain text pages of normal-size print, 200 dpi in B/W mode was
adequate, while 300 dpi looked as good as any photocopier.

I'm assuming the PS7000 is a more recent model.  If the PS7000 is
newer, then Minolta seems to have gone backward, not forward.  The
PS3000 will scan at 400 dpi max, while apparently the PS7000 will only
scan at 300 dpi.  The PS3000 does have a "book correction mode" which
works well to eliminate distortion due to curved pages in bound
volumes, while the comment below says the PS7000 does not offer this.
Both can scan documents, or facing pages, up to a total dimension of
11"x17".  The PS3000 manual claims it can achieve acceptable "depth of
field" up to four inches above the copy deck, and this seems to be the
case.

While the three compressed TIFF modes vary in file size, there's no
difference in the quality of the scan, and no difference in a file
saved in these formats then re-opened.  The three TIFF modes are Group
3, Group 4, and something called JBIG.  Generally, JBIG gives slightly
better file compression, if that's an issue, and I understand that
Group 3 has been superseded by Group 4 (and maybe Group 4 has been
superseded by JBIG).  I've also heard that not all programs can read
JBIGs, but MS Photo Editor has no trouble with it, and that's about as
"low-end" as you get in image editing software.

I have it on good authority that Minolta is purposely remaining
"behind the curve" in adding improvements to this line of scanner. I
don't know whether this is because they have no direct competition
with this type of device, or whether there's just not a large enough
market to justify a major research-and-development effort.

My conclusion is that you could certainly get a better scan from a
$300 flatbed scanner (along with color) but for materials that are too
fragile to go face down on a scanner or standard photocopier, the
PS3000 is an acceptable substitute if you need its special
capabilities.  If you never need to scan fragile volumes, get the
flatbed scanner and don't give the PS3000 (or PS7000) a second
thought.

On Fri, 8 Dec 2000, Chuck Thomas wrote:

> 1) it's incapable of color scanning, only grayscale at a max resolution of
> 300 ppi.
>
> 2) it CAN handle document larger than your typical flatbed scanner
>
> 3) the focus mechanism cannot handle rippled, curved paper surface very
> well on flat pages. It will focus on one height, and cause some blurring on
> the indentations or "valleys" in rippled documents.
>
> 4) The illumination light on the PS7000 is VERY hot, and certainly causes
> more light damage to a document than does a traditional flatbed scanner. I
> joke with my students that we need to keep suntan oil close by when using
> the machine:) The tradeoff is that you can scan books that never before
> could be scanned without spinal damage.
>
> Perhaps you could explain exactly what documents need to be scanned. If
> flat paper document smaller than 11 x 17" (including photographs) are what
> you need to scan, then you can find an excellent color-capable flatbed
> scanner for much less money.
>
> In our digital imaging lab here at the University of Minnesota, we have not
> one but two (liked the first one so much I bought another) Epson Expression
> 836 XL scanner, that do a remarkable job of producing photo-quality scans.

=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=

James Stimpert                       E-mail:    James.Stimpert@jhu.edu
Archives (Arts and Sciences)
MSE Library
Johns Hopkins University             Voice:     (410) 516-8323
3400 North Charles Street
Baltimore, MD  21218                 Fax:       (410) 516-7202

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