Re: Scanners?

[" Raymond A. Ingles" <inglesra@frc.com>]

On Wed, 8 Apr 1998, Don Berkich wrote:

> I'm looking for advice on what flat-bed SCSI scanner to
> buy;  something in the $200 - $400 price range, if
> possible.  I've got Debian 1.3.1 on a Cyrix-166 machine
> currently, but I'll soon be upgrading to a dual PII-300.
> 
> Advice on what scanners to avoid would also be most welcome.

 The first thing to know about scanners and Linux is that
"TWAIN-compliant" means nothing as far as Linux is concerned. It's a
software-only, Windows-specific standard that is worthless under Linux.

 A better standard is being developed, called "SANE". (It stands for
"Scanner Access Now Easy". Don't blame me, I didn't make up the acronym.
:-> ) The project's webpage is at "http://www.mostang.com/sane/";. This
also provides a list of supported scanners.

 Specific scanner models are supported by various special-purpose
packages, e.g. "mscan" for Mustek scanners. Take a look at sunsite,
somewhere there's a "scanner" directory.

 If you want to go commercial, I understand that XVscan is pretty good. It
adds scanning capability to XV. Last I heard it only supported HP
scanners, but that may have changed.

 General tips on scanners:

 1. If you can possibly afford it, get a SCSI scanner. The interface is at
least twice as fast as a parallel port, and it consumes far less CPU while
you're scanning. In addition, more SCSI scanners are supported under Linux
than parallel port models.

 2. Some cheaper SCSI scanners, e.g. Mustek and Microtek, don't support
the SCSI-II "disconnect" feature. This means that while you're scanning,
the SCSI bus is locked.

 3. The SCSI cards that come with most scanners are total crap, and even
if you can beat them into submission and get them to work under Linux,
they will perform terribly poorly.

 4. Because of 2 and 3, it's adviseable to get a separate SCSI card just
for the scanner (or get a more expensive scanner that disconnects, e.g.
HP). You can get an NCR PCI SCSI controller for $50 these days, so this is
not a big problem. I have a SyQuest drive and my Mustek scanner on the
same SCSI bus, but I had to hack the scsi driver to increase the disk
timeout. Otherwise, I couldn't use both at the same time.

 5. If you're just scanning for personal use, and maybe to put things on
the web, any resolution above 300dpi is overkill. Web images usually have
to be small to be useful, and even at 256 colors (1 byte per pixel), a 4x5
inch picture becomes a 1.7MB file at 300dpi. If you scan in 24bit color,
you get a 5MB file. Saving in compressed formats like gif or jpg will
help, but even so you'll rarely scan anything over 150dpi.
 Of course, if you're going to use this for a business, for say
camera-ready art or something, 600dpi should be the *minimum* to look at.

 6. As to number of colors, a personal user doesn't need any more than
24-bit color. Business or scientific users might need 30-bit color, but a
lot of applications can't even handle that kind of data anyway.

 Sincerely,

 Ray Ingles         (248) 377-7735          ray.ingles@fanucrobotics.com

 "Anybody who has ever seen a photograph showing the kind of damage that
  a trout traveling that fast can inflict on the human skull knows that
  such photographs are very valuable. I paid $20 for mine." - Dave Barry


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