[sane-devel] More front end developer Q's

khk at khk.net khk at khk.net
Mon Sep 22 12:27:35 BST 2003

>[ ... ]
> For my EPSON GT-7000, the epson backend returns resolutions up to 2400,
> and
> a default of 50. However EPSONs docs say the native resolution of the
> scanner is 600 dpi.

And that's true, the optical resolution of the scanner is indeed 600 dpi,
but the the EPSON scanners that support ESC/I (that's their control
langauge) have a command that requests the resolutions that the scanner
can provide. The GT-7000 does report resolutions above 600 dpi, and I
have no way of knowing if a given resolution is interpolated, or native.

There is however a difference between the main- and sub-scan directions:
The main scan direction (that is the direction in which the sensor is
aligned), the optical resolution of 600 dpi is the limit, in the sub
scan direction (the direction in which the sensor is moved by stepper
motors), the optical resolution does not apply: The scanner can move
the sensor by smaller steps, so that the resolution is actually

This means that when you ask for a 2400 dpi scan, you should get a
slightly better scan than if you select 600 dpi. At least in theory:
It all depends on the shape and size of the sensors.

Karl Heinz

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