Re: vision range
Re: vision range
- Subject: Re: vision range
- From: Ray Maxwell <email@hidden>
- Date: Mon, 26 Nov 2001 16:59:14 -0800
"Michael S. Dodds" wrote:
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Good morning,
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Has anyone seen any papers concerning
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the number of colors generally believed
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visible and to a human standard observer?
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If not - any opinions?
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MSD
Hi Michael,
I have seen this question many times and I have seen many different answers.
The human eye has three types of color detectors called cones. They
are, roughly speaking, sensitive to red, green, and blue light. When
combined they are sensitive to electromagnetic radiation from 700
nanometers to 400 nanometers.
Now, how do we define one color that can be counted. How do we know
when we can say that we have moved from one color to another color in
our count. Should we define it in wavelengths of light? Should we also
consider luminance? Should we count how many colors can fit in the
human perception space that are one delta E from each other? Should we
use delta E or CIE Delta E CMC?
The human perception of color is a continuum. It is an analog sensor.
I don't think that it has any meaning to say how many colors can a human see.
I do think we can define the color resolution of digital printing
systems and I do think that it should be able to step though the human
perception range smoothly. A eight bit per color RGB system seems to
produce smooth transitions. This system can produce 256 x 256 x 256 (16
million) colors. However, in the CMYK world we usually only have 100
steps for each subtractive primary and black. Note that there are many
combination of CMYK that produce the same color. So one cannot take 100
x 100 x 100 x100. If we only use CMY we get about one million colors.
This produces smooth gradients over the limited dynamic range of a
printing system.
I have seen people demonstrate that for a typical density range of
printing and photographs a smooth gradient can be produced with as
little as 40 steps. This also depends on the physical width of each
step. Keep in mind that the eye has a much wider dynamic range than a
printing system or photographic system.
To summarize, I don't think there is an absolute answer to this question.
Ray
--
Ray Maxwell
Color Systems Engineer
CreoScitex
4225 Kincaid Street
Burnaby, B.C.
Canada V5G 4P5
Phone (604) 451-2700 ext. 2004
| References: | |
| | >vision range (From: "Michael S. Dodds" <email@hidden>) |