Chuck Norcutt wrote:
> Why are you so positive that it's software? One would hope that's the
> case since that's easily corrected. However, I could hypothesize that
> there is/was a mechanical glitch in the sensor bar transport such that
> the sensor wasn't where the software thought it was. Why couldn't this
> be so?
>
It could be such a thing, although the symptoms would seem to require
some unlikely malfunctions. I believe these mechanisms do not have
absolute positioning. They simply run back to the stop and keep track of
their position during scanning by counting stepper motor impulses from
zero. I rather doubt if they are even able to move backwards with
precision. Listen to and watch one as it scans. It simply moves forward
steadily at the rate necessary for the resolution chosen. It may go at
its highest forward rate to pass over areas not needed before starting
the actual scan process, and stop scanning at the end of the scan area,
but the scanning process is forward at a steady pace.
So how then do we get to the symptoms of the same parts of the same
frames turning up in multiple output files?
The basic scanning process produces a raster image of the full width of
the length of platen scanned. It is then the software that selects
portions of the raster image to process into output files. So the most
likely cause of the described symptoms is messed up parameters in the
scanning software, causing it to select the wrong part of the overall
raster image. The apparent repeatability of the symptoms going down the
platen and with each different scan pass also make me suspect this.
Empirically, I recall Vincent Oliver running into related sounding
symptoms in some of his flat bed scanner reviews which were software
issues. Also, when testing the transparency scanning capability of a
Canon 5000F with VueScan, I had some problems with messed up frame
coverage and provided Ed Hamrick with data and output that he used to
fix the parameters for that scanner in VueScan. Play with the custom
scan parameters in VueScan and you will get an idea of how it works and
how easy it is to screw up.
So sure, maybe hardware/firmware, but my bet is software.
John, have you made sure you have the latest version of the software you
are using? If so, a reinstall may help if a parameter table has been
compromised.
Moose
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