re: 16 bits = 15 bits in Photoshop?
re: 16 bits = 15 bits in Photoshop?
- Subject: re: 16 bits = 15 bits in Photoshop?
- From: Richard Wagner <email@hidden>
- Date: Wed, 13 Apr 2005 12:44:17 -0700
Not quite, John.
2^0 is one, not zero, and zero is the "darkest dark." For an n-bit
unsigned integer, 2^n gives the number of levels, and 0.. 2^n-1 gives
the range.
In an 8-bit unsigned integer, there are 2^8 = 256 levels: 0, 1, 2,
...255.
PS does not use a simple, unsigned, 16-bit word for high-bit data, or
the number of levels would be 2^16 = 65,536, with a range from
0..65,535.
If PS used an analogous representation for 8-bit data, there would be
2^7 = 128 levels.
--Rich Wagner
"0" is one of the values of a 16-bit file, so the brightest white would
only go to 2 to the power of 15.
In other words, the values go like this:
1. 2 to the power of 0 darkidiest dark
2. 2 to the power of 1
3. 2 to the power of 2
4. 2 to the power of 3
5. 2 to the power of 4
6. 2 to the power of 5
7. 2 to the power of 6
8. 2 to the power of 7
9. 2 to the power of 8
10. 2 to the power of 9
11. 2 to the power of 10
12. 2 to the power of 11
13. 2 to the power of 12
14. 2 to the power of 13
15. 2 to the power of 14
16. 2 to the power of 15 whitiest white
See?
John MacDonald
Dodge Color, Inc.
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