Re: HP ScanJet IIc ADF report

Nick Lamb (njl98r@ecs.soton.ac.uk)
Tue, 16 Mar 1999 00:30:06 +0000 (GMT)

On Mon, 15 Mar 1999, Peter Kirchgessner wrote:

> the HP ScanJet IIc has an optical resolution of 400 dpi. All other values
> are interpolated. The scanner can do an interpolation for 12 to 1600
> dpi.

This doesn't match up very well with my actual experience of using the
scanner. I suppose it's possible (but unlikely) that it is broken...

Here are some example results (happily scanned with the new XSane release)
they are all for _exactly the same physical scan area_

400 dpi color scan --> 364 x 374 image
600 dpi color scan --> 546 x 560 image
800 dpi color scan --> 728 x 747 image
900 dpi color scan --> 720 x 740 image (!)
1600 dpi color scan --> 728 x 747 image (!)

I don't particularly care whether the scanner has an optical resolution of
400 dpi, 800 dpi or even 1600 dpi for that matter. But I do know that the
SANE backend never gives me more 728 x 747 (which is 800 dpi exactly)
no matter how high a resolution I choose from scanimage or XSane.

I've just tested in Windows, and there I can do a 1600dpi scan but as you
say, this is interpolated data, and by 1600dpi it's becoming rather too
obvious that most of the data is a fairy tale (15 made up pixels for each
one read by hardware I guess).

So, I suppose I'd like (1) An HP backend fix if applicable, and (2) Some
future SANE standard to include Optical Resolution where known, so that I
don't waste my SCSI bandwidth on interpolated data :)

If this problem can't be diagnosed remotely, I'll look at it on Sunday.

Nick.

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