Re: Which scanners REALLY provide 36 bit output? HP?

From: Stephen Williams (steve@icarus.com)
Date: Tue Dec 12 2000 - 11:56:49 PST

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    s57uuu@hamradio.si said:
    > (Yes, it's 3 - the luminance sensors (the 'rods') have the same
    > sensitivity as the 'green' channel 'cones')

    Not quite, they respond to a wider spectrum then the green sensors.
    Though they are highly sensitive to green, they respond to most all
    of the visible color range. I think.

    (Actually, after saying that I'm not really sure how wide the spectral
    response is for luminance, but I do know that luminance calculations
    certainly all include some red and blue, and I presume there is a
    psychological/physiological reason for that.)

    s57uuu@hamradio.si said:
    > Back to scanning - if you need to get all the info that is in a
    > photograph ABOUT THE ORIGINAL SCENE, a three channel scanner is
    > enough, because the original photo process has already reduced it to 3
    > chans.

    But do the spectra of those three channels cause the RGB sensors in
    your scanner to respond similarly? That's a question for a photography
    expert, I think. All I know is that it can be a real chore finding the
    right combination of light, sensor and filters just to get white paper
    to come out right. Been there, struggled with that.

    -- 
    Steve Williams                "The woods are lovely, dark and deep.
    steve@icarus.com              But I have promises to keep,
    steve@picturel.com            and lines to code before I sleep,
    http://www.picturel.com       And lines to code before I sleep."
    

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