# Re: Problem with scan quality using UMAX Astra 1220S

From: Oliver Rauch (oliver.rauch@Wolfsburg.DE)
Date: Fri Nov 03 2000 - 15:19:12 PST

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  Rod Pike wrote:
  >
  > Greetings,
  >
  > I'm running RH 6.2 and using the supplied version of Gimp and sane-1.0.1-4. I
  > have a problem getting output from this combination that comes close to the
  > quality of the output I get using the supplied Windows Twain interface (
  > VistaScan ) that came with my UMAX Astra 1220S.
  >
  > The problem is difficult to explain but if you look at these jpegs I think you
  > can see what I mean. There is a faint line of pixels on the xscanimage
  > captured image and it's hard to see here but the uniformaty of the pixels on
  > the vistascan captured image is much smoother than that of xscanimage.
  >
  > http://www.iosphere.net/~sullivan/rp/sane/vistascan300dpiRGBcrop.jpg
  > http://www.iosphere.net/~sullivan/rp/sane/xscanimage300dpiRGBcrop.jpg
  >
  > Both images are scanned using the same source at 300 dpi. I've used whatever
  > default settings there are with each interface.
  >

  Hi Rod,

  this looks like a problem of your scsi bus or drivers.

  Here is a part of the xsane helpfiles:

  The scanner starts the scan but it stops while scanning
  The scsi bus or the whole system freezes
  The image is corrupted

  In general there are three different reasons that can cause such erros:

  In most cases it is a problem with your scsi bus. Please check the following points:

  The scsi bus has to be a chain (one line) that is terminated on both ends. If possible the
  scanner should be on one end of the chain because the connectors on most scsi
  scanners are not specified for the scsi-2 standard.
  If you do not use any ultra-scsi-devices and your scsi controller is a fast scsi
  controller you can use passive terminators. If one or more devices are
  ultra-scsi-devices you have to use active terminators.
  If the scsi controller is at an end of the scsi chain the termination of the controller has
  to be enabled. Otherwise it has to be disabled. If you use a fast scsi controller and you
  have one or more ultra-scsi-devices connected, you must not use the built in
  termination of the scsi controller (because it is a passive terminator), you have to use
  an active terminator instead.
  The length of the scsi chain is limitted. If you use no ultra-scsi-devices the whole
  length of the chain must not exceed 3 meters. If there are one or more
  ultra-scsi-devices in the scsi chain the length of the chain must not exceed 1.5
  meters. If there are only 3 devices (2 devices + controller) the length of the chain
  may be up to 3 meters, but if you have any problems you should try to reduce the
  length.

  The driver for your scsi controller does not work like expected. Update your scsi driver if you do not
  have the most recent version.
  If that does not help try it with an other type of scsi card.
  May be your scanner/firmware does not work correct with the backend you use. Update the
  backend version or contact the author of the backend.

  May be that helps

  Bye
  Oliver

      --
      Homepage:	http://www.wolfsburg.de/~rauch
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