16 bits = 15 bits in Photoshop?
16 bits = 15 bits in Photoshop?
- Subject: 16 bits = 15 bits in Photoshop?
- From: Marco Ugolini <email@hidden>
- Date: Wed, 13 Apr 2005 01:03:05 -0700
I just saw this question posted on an Italian color management site
(<http://it.groups.yahoo.com/group/colore_digitale/messages>), and I myself
don't have an answer for it.
Here is the background for the question:
- Open a new 16-bit file in Photoshop CS 1 (it doesn't matter whether in RGB
or Grayscale or Lab) and create a gradient from black to white.
- In the info palette, choose "Palette Options..." from the submenu in the
palette's upper-right-hand corner, and make sure to check the "Show 16 bit
values" check box, then click "OK."
- Also make sure that "16 bits" is checked in the eyedropper submenu in the
info palette's section where the the actual values are shown.
At least in theory, a 16 bit image ought to have values ranging from 0 to
65536 (65536 = 2 to the power of 16), but if you use the eyedropper tool in
Point Sample mode and roll the mouse pointer over the values in the image
created above, you will see that the brightest white has a value of only
32768 (32768 = 2 to the power of 15, not 16).
So, the question is:
Is the 16-bit mode in Photoshop CS 1 really 15 bits? And is this still the
case in Photoshop CS 2?
Thank you for any input you may have.
--------------
Marco Ugolini
Mill Valley, CA
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