White Point & Black Point

Discussion in 'Photoshop' started by frankg, Oct 17, 2005.

  1. frankg

    frankg Guest

    I've been asked for some stock images, and for them to be scanned with a
    White point of less than 252 and a Black point no less than 3.
    This keeps the rgb values slightly less than the full 256 range, and helps
    limit extreme values that will not print. And it helps limit errors when
    values fall outside the boundaries of an 8 bit file.
    However, I have some files that are already scanned and saved as 16 bit. I
    do not want to have to go back and scan again, so how do I accomplish the
    same in PS?
    Do I go to Levels and move the bottom Output Levels slider in at both ends
    by 3 points?
    And if so, is this only true for files which have the Levels histogram
    showing
    that the values touch the end on one or on both sides ? If they dont touch
    the
    end then they're less than the maximum/extreme of 0 & 256 anyway - correct?

    =========
     
    frankg, Oct 17, 2005
    #1
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  2. You can do that, but if one or both ends are clipped, it only means you
    push the clipped values inwards. It doesn't give you back the detail
    that was clipped.
    Correct.
     
    Johan W. Elzenga, Oct 17, 2005
    #2
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  3. frankg

    frankg Guest

    but on Curves for example, if you grap the very top (highlight) of the line
    and drag it straight down, then you bring down that value, from 256 to
    whatever. And conversely for the black or bottom of the line
     
    frankg, Oct 17, 2005
    #3
  4. frankg

    DD Guest


    somebody recently said something of great value here (could have been
    tacit,and it sounded as if it was a relieve for the Kat as well);
    something to the effect that,* ìf the colours are not clipped*, and
    said points is not moved out of their corners, the colours can not be
    clipped via the curve dialog. Sometimes I lean heavy on this advice.

    Dave
     
    DD, Oct 17, 2005
    #4
  5. Correct, but that is the same as using Levels, and also with the same
    restrictions.
     
    Johan W. Elzenga, Oct 17, 2005
    #5
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