Re: 8 bit vs. more bits
Re: 8 bit vs. more bits
- Subject: Re: 8 bit vs. more bits
- From: Robert L Krawitz <email@hidden>
- Date: Sun, 17 Apr 2005 21:14:15 -0400
From: "Mark Rice" <email@hidden>
Date: Sun, 17 Apr 2005 20:46:33 -0400
There certainly have been a lot of specious and non-scientific
arguments on this subject lately.
I would like to establish several things:
1. Viewing a monitor to detect differences in 8 bit vs. more bits
is a thankless task. Have you ever asked yourself, how can I get
the 16.7 million colors promised by 8 bit (or 24 bit for 3 colors)
from only 1024 lines of video resolution? YOU CAN'T!!!. We simulate
it with dithering.
The acid test here is displaying a green ramp from 0-255. Can you see
the transitions? When I've tried it, the answer is yes, and to me at
least that means that the resolution, even at the output, is too
coarse.
2. Can a color printing device display 16.7 million colors? Not
likely. The Durst Lambda, at 400 dpi, would need to make a print
3,479 FEET long in order to use all 16.7 million colors! So
dithering is also used in printing devices.
Again, the real question is whether you can see a stairstep effect.
Not to mention that that calculation is incorrect -- at 20,000
points/square inch (the Lambda is continuous tone, right?) it would
take about 850 square inches to print 16.7 million pixels, each of a
different color. But that's a red herring -- the issue is whether you
can see transitions between particular colors that you care about, not
how many different colors can be printed on a print of a particular size.
Both of the above statements are true, and I suspect that is where
Dan M's reasoning coming from. If one takes a perfectly exposed
digital photos, or makes a flawless scan utilizing the entire 256
bit range, than no higher bit depths are necessary.
I doubt very much that that's what Dan means. Photos aren't usually
the acid test for high bit depths, although I've taken a few
photographs where you can see the stairsteps in the sky at 8 bits of
precision. A better test would be a logo with a gradient from, say, a
medium green to a light green, where the range of colors you care
about is very small but it's essential to have transitions that are
perceptably perfectly smooth. The example of the sky, of course, is a
gradient.
--
Robert Krawitz <email@hidden>
Tall Clubs International -- http://www.tall.org/ or 1-888-IM-TALL-2
Member of the League for Programming Freedom -- mail email@hidden
Project lead for Gimp Print -- http://gimp-print.sourceforge.net
"Linux doesn't dictate how I work, I dictate how Linux works."
--Eric Crampton
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