how do you display 16 bit info on 16 bit images?

Discussion in 'Photoshop Tutorials' started by WD, Jul 25, 2004.

  1. WD

    WD Guest

    Folks,

    Question. When I work on 16 bit images, all curves info etc. still
    display as if the image is an 8 bit image. (Photoshop CS on Windows XP).
    Is there a way to have the various data displays show as 16 bit
    values (i.e. 0-65536 vs. 0-255)??

    Thanks

    W
     
    WD, Jul 25, 2004
    #1
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  2. Select options of Window|info palette, tick "Show 16 bit values".

    Bart
     
    Bart van der Wolf, Jul 25, 2004
    #2
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  3. WD

    WD Guest

    Bart,

    Thanks. That worked for 'info'. Is there anything that can be done
    regarding curves or histograms?

    Also, the max value is 32768 and not 65536, do you know the reason for this?

    Thanks again

    W
     
    WD, Jul 26, 2004
    #3
  4. WD

    Mike Russell Guest

    Photoshop's 16 bit format ranges from 0 to 0x8000, using just one value more
    than 15 bits. The remaining values are not used. Just a guess, but perhaps
    they are used for intermediate values in image calculations.

    I've considered adding 16 bit display to Curvemeister. It's a reasonable
    request, but there has been no request for it.
     
    Mike Russell, Jul 26, 2004
    #4
  5. Not with a Photoshop setting, but there is a free histogram "filter"
    available at:
    http://www.reindeergraphics.com/free.shtml#widehisto
    It also shows that to display (and select ranges) more than 256
    values, one needs a wide histogram to really benefit. Curves are too
    crude to need 15-bit precision, you'll need a different application if
    you need that type of accuracy.
    for this?

    That's how it is in Photoshop. The final high bit is used for
    calculation overflow. It allows calculations (including rounding and
    multiplications) to be done with 16-bit integer math, which is
    presumably quicker in most processors than 32-bit math (or you could
    do 2 multiplications at the same time).

    Bart
     
    Bart van der Wolf, Jul 26, 2004
    #5
  6. WD

    Xalinai Guest

    The reason ist that you are working with Photoshop.

    According to the PS gurus here this is not a bug but PS works as
    designed.

    They didn't mention why there is no limit of 128 in the eight-bit
    version. :)

    Michael
     
    Xalinai, Jul 26, 2004
    #6
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