Re: some technical questions

Date: Fri Jan 19 2001 - 08:02:47 PST

  • Next message: Henning Meier-Geinitz: "Re: some technical questions"

    On Thu, 18 Jan 2001, Henning Meier-Geinitz wrote:

    > Hi,
    > 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.

    That's exactly how it is here as well.

    > > * 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).

    I don't think it's worth trying to find out then.
    It is a USB scanner. It has bandwidth problems at 600x600dpi already.

    > > * 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.
    Could you e-mail me a link ?

    > > * 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.

    Yep. Also - is there any central place I could store the test program I
    wrote ? Instead of starting yet another project on Sourceforge.

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

    Have no idea. I have not seen similar scanner though, so it must be them.
    It is actually a very nice scanner (2400x1200) and is completely USB
    powered. One drawback are some kind of moire pattern when you scan black
    and white line art (though one can get rid of it rather easily).

                                 Vladimir Dergachev

    > Bye,
    > Henning
    > --
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