Question about the ability of human visual system

Discussion in 'Optometry Archives' started by jogging, Jun 21, 2011.

  1. jogging

    jogging Guest

    Hi, all

    From Digital Image Processing(Third Edition) by
    Rafael C. Gonzalez and Richard E. Woods,
    it reads
    " human can discern thousands of color shades
    and intensities, compared to about only two
    dozen shades of gray. "

    What does it mean? For an image with its
    values in the range between 0 and 255,
    does it mean that human can't discern the
    difference between two grayscale values
    whose difference is smaller than 10(256 / 24
    is about 10)?

    I do an experiment. With the background of 150,
    a block is placed in the middle of the image
    and its value is 151. I can't discern the difference.
    If I change the value of the block from 151 to 152,
    I can discern the existence of the block easily.

    Can anyone provide any books or links on it?

    Best Regards
    jogging, Jun 21, 2011
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