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 14:34:15 -0700
Bruce wrote:
Either Chris made a typo or something got lost in the translation.
15 bits lets you represent 32,768 levels.
Photoshop's 16-bit implementation allows 32,769 levels, from 0 to
32,768.
You can't represent 32,769 levels with 15 bits, you need 16.
And that is the key.
What they currently represent is 15 bits plus one.
You can't count from 0 to 32,769 with 15 bits. Yes, they use "all" 16
bits, but no, they don't use the entire range of numbers possible with
16 bits. As you "go up the ladder" they stop counting the moment the
16th bit gets set. There's no value represented by, for example,
1000...01 or 1000..10 or all 1's.
If you open a full-range 16-bit image, it gets reduced to the 15.1
format in PS.
While this "limitation" has apparently given a huge advantage with the
speed of the math, who knows if this speed increase will be important 3
or 5 or 10 years from now. I believe Phase One digital backs are
true16-bit/channel, as well as many scanning backs and even the Imacon
scanners. In the old days, we used Indexed Color... then were thrilled
with 8-bit/channel. Time will tell.
--Rich Wagner
_______________________________________________
Do not post admin requests to the list. They will be ignored.
Colorsync-users mailing list (email@hidden)
Help/Unsubscribe/Update your Subscription:
This email sent to email@hidden