Re: some technical questions

From: Henning Meier-Geinitz (hmg-ml@gmx.de)
Date: Thu Jan 18 2001 - 14:04:58 PST

  • Next message: Henning Meier-Geinitz: "Re: Lifetec LT9385"

    Hi,

    On Thu, Jan 18, 2001 at 03:54:31PM -0500, volodya@mindspring.com 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
    duplicated.

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

    Bye,
      Henning

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