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

From: Stephen Williams (
Date: Tue Dec 12 2000 - 11:56:49 PST

  • Next message: Tobias Nijweide: "HP5300C mini HowTo" 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.) 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.              But I have promises to keep,            and lines to code before I sleep,       And lines to code before I sleep."

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