Re: 8-bit vs 12-bit

From: Oliver Rauch (oliver.rauch@Wolfsburg.DE)
Date: Sun Jan 16 2000 - 10:53:12 PST

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    Rick Rosinski wrote:

    > What is the difference between 8-bit and 12-bit images?
    > I notice that it takes twice as much space for a pnm file under 12-bit vs 8-bit.
    >
    > When I used Sane 1.00 under SuSE 6.1, I was able to scan (xscanimage) 12-bit
    > images and view them in GIMP. But when I tried Sane 1.0.1 with Umax 1.0.1
    > back-end (Umax Astra 1220s), I was only able to scan in 8-bit mode. 12-bit
    > yielded purple text and green background. 8-bit looks good.
    >
    > Ultimately, I will be using xscanimage to scan photographs. I have many photos
    > stored under 12-bit graphics, which were converted to JPGs, but now I cannot
    > scan in 12-bit. I would rather scan in 12-bit just to make sure that the
    > photos are the best they can be?
    >
    > What is the difference, and is there a way to get Sane 1.0.1 to do 12-bit like
    > 1.0 did?
    >
    > I am using Umax Astra 1220s on a Slackware 7.0 system.
    >

    Hi Rick,

    1) xscanimage does not support 12 bpp (16bpp) at all, if you got a good looking
    output with it that was luck.
    2) if you do not know for what it is good you simply don`t need it. Displays and
    graphic programs normally work with 8(24) bpp. A printer is not able to
    make visibile all information that are in 8/24) bpp.
    Only if you want to do "hard" color correction AFTER scanning it could get relevant.
    3) Try xsane if you really think you need it.

    Bye
    Oliver

    --
    Homepage:       http://www.wolfsburg.de/~rauch
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    E-Mail:         mailto:Oliver.Rauch@Wolfsburg.DE
    

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