Re: some technical questions

From: Henning Meier-Geinitz (
Date: Thu Jan 18 2001 - 14:04:58 PST

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    On Thu, Jan 18, 2001 at 03:54:31PM -0500, wrote:
    > * I think I found 3 sets of data that looks like gamma. Does it make
    > sense ?

    Yes, that may be ok for color mode. Most scanners I use have 4096
    bytes of gamma (per color) so they use a mapping of 4096->256.

    > * The scanner is said to be 30 (or 32 ?) bit but I only get 24bit data
    > is it supposed to be so ?

    That's probably marketing speech. The 30 (or 36, 48) bits are used
    internally. After calibration + gamma correction 24 bits are returned
    to the computer. Some scanners allow to transmit the raw data with the
    higher bits/pixel but then calibration/gamma isn't used (at least in
    my experience).

    > * there are also some registers that drive the motor - I can use them
    > but if there are some general ideas about how they should work I'll
    > be happy to listen

    That's quite dependent on the chip the scanner uses. Maybe it helps to
    look at a paper about stepper motors.

    > * I don't understand how sensor is switched from 75dpi mode to higher
    > dpi mode. (i.e. I can drive the carriage at different resolutions,
    > but I don't know how to get the sensor to output higher precision
    > data)

    As far as I see at the Mustek scanners the sensor always scans at the
    maximum resolution. Only the data is reduced somewhere in the scanner
    when lower resolutions are used.

    Can I add an entry in the PROJECTS file of SANE for you? So no work is

    Is the chip(set) used by canon produced by them or from another vendor?


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