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Q: Amount of colors that can be differentiated ( No Answer,   10 Comments )
Question  
Subject: Amount of colors that can be differentiated
Category: Science
Asked by: uksearcher-ga
List Price: $5.00
Posted: 30 Jul 2004 11:24 PDT
Expires: 29 Aug 2004 11:24 PDT
Question ID: 381379
hi,

i am looking for the total amount of visible colors - both
transmissive and reflective - that can be differentiated by a typical
standard human being. the result must be scientifically proven and
should indicate as to how the testing was executed.

Clarification of Question by uksearcher-ga on 10 Aug 2004 12:45 PDT
hi,

thanks for all the efforts. unfortunately it looks as if there doesn't
seem to be a scientifically proven test yet as to how many colors a
typical standard human being can differentiate.

i am aware that each human being of course is unique hence the
capability of differentiating colors might vary from person to person
to a certain degree. however, i don't believe that the differences are
that big as the last comment might indicate.

otherwise it would be interesting to have scientifically tests that
can prove otherwise.

anyway i was looking for a typical standard human being 
(btw, the total amount of rgb pixels with different values on screen
are over 16 million and not 1.68 million as indicated).

thanks again for all your efforts. maybe, we will find the answer.
Answer  
There is no answer at this time.

Comments  
Subject: Re: Amount of colors that can be differentiated
From: monroe22-ga on 30 Jul 2004 11:42 PDT
 
Dear uksearcher: I was a professional color matcher in the coatings
industry. The *estimated* number of visibly perceived colors is said
to be more than one million, so it may be difficult to obtain a
precise, scientific answer, in part because of the difficulty in
defining a typical standard human being. There is a rather wide range
of ability to perceive small color differences among persons with
normal vision. However, today most color matching is done with
colorimiters, such as the Hunter model. Perhaps the manufacturers of
those instruments can state the range of their product with precision,
but that would not answer your question. Interesting question...good
luck.
Monroe22-ga
Subject: Re: Amount of colors that can be differentiated
From: uksearcher-ga on 30 Jul 2004 11:54 PDT
 
hello, 

thank you for your reply and your wishes. i am aware of the use of
colorimeters and also delta e which unfortunately doesnt provide an
answer to the question. but let us see.
Subject: Re: Amount of colors that can be differentiated
From: monroe22-ga on 30 Jul 2004 19:28 PDT
 
uksearcher: Delta e is a numerical value which is very helpful in
defining color difference from a given standard, but has no relation
to your question, which is indeed very interesting. As one who has 45
years of experience in both visual and colorimetric color matching, I
look forward to an answer to your question. By the way, for me, it is
painful to admit, instrumental color matching is vastly superior to
the human eye. The colorimiter is much more sensitive than the eye.
Monroe22
Subject: Re: Amount of colors that can be differentiated
From: uksearcher-ga on 31 Jul 2004 03:07 PDT
 
hello, 

please correct me if i am wrong, but delta e has indeed a very strong
relation to my question as it is a scientific expression as to how
different colors look to the human eye. if delta e is less than 1 then
colors look identical to the human eye. in other words delta e=1
should not just "in my eyes" be the threshold for any scientific
testing.

thanks for any advice
Subject: Re: Amount of colors that can be differentiated
From: meesadesiking-ga on 01 Aug 2004 13:16 PDT
 
Total color difference is the distance between a standard and a trial
in a given color space. Total color difference in a color space is
called "Delta E" ) and is always a positive value ( a negative
distance has no meaning). Delta E only tells the total color
difference, not the direction of the difference. For example, two
colors can have the same Delta E, but one could be dark and green and
the other one could be light and red). So I hope you realize that
delta E has pretty much no relation to your question..

If you were to think of probability, I can propose a way.
Though there are no exact bounds to the optical spectrum ; a
light-adapted eye typically has a maximum sensitivity of ~555 nm (in
the green). Commonly the response of the eye is considered to cover
380 nm to 780 nm although a range of 400 nm to 700 nm range is more
common. The eye may, however, have some visual response at even wider
wavelength ranges.
Now another thing is that the human eye can distinguish any light
change where the frequency differnce is lower than 60Hz .. ie the time
period is 1/10 of a second. If you multiply this time period with the
speed of light, you can get the minimum change in wavelength the
normal human eye can detect. Divide the maximum senstivity range
(555nm) with this number you get and you should be able to get the
maximum number of colors the human eye can detect clearly.. my
calculations lead me to number close to 20,000 colors.
Subject: Re: Amount of colors that can be differentiated
From: kulnor-ga on 02 Aug 2004 12:06 PDT
 
The following information can be found on the Munsell Color Science
Laboratory, MCSL (http://www.cis.rit.edu/research/mcsl/) at
http://www.cis.rit.edu/mcsl/faq/faq1.shtml#q11
Hope this helps.

==============================================================================
This is a very popular question and it is usually answered vaguely by,
"Millions and millions!" However, it is better to ask the question in
a more specific way to get a more comprehensive answer.

Many of us can select a setting for our computer monitors that
displays millions of colors and we see an improvement in image quality
with this setting. However, if you select the colors correctly you can
reduce the number of colors to a couple of hundred or even fewer
(depending on the image) without noticing a degradation in quality.
This would indicate that we can't see millions of color variations
simultaneously.

One way to answer the question is to measure the ability of people to
discriminate colors. Many researchers have investigated chromatic
discrimination by varying the wavelength of two monochromatic lights
until they are just noticeably different. Other studies have used the
variability of color matching to gauge discriminability and yet others
have directly measured threshold differences throughout color space.
Using these measures we find that our visual systems can discriminate
millions of colors.

In our laboratory we are interested also in larger than threshold
color differences: the type of differences that would make you reject
a certain touch-up paint because it's not a close enough match to the
color of the paint of your car. Even with such a metric there are
close to a million discriminable colors on a computer monitor which
only can reproduce a fraction of the colors we can see out in the real
world.

References
1) G. Wyszecki and W.S. Stiles, Color Science: Concepts and Methods,
Quantitative Data and Formulae 2nd Ed., Wiley, New York, 1982.
2) R.W.G. Hunt, Measuring Colour 3rd Ed., Fountain Press, England, 1998. 
3) R.M. Boynton, Human Color Vision, Special Limited Edition, Optical
Society of America, Washington D.C., 1992.
4) M.D. Fairchild, Color Appearance Models, Addison-Wesley, Reading,
Massachusetts, 1998.
Subject: Re: Amount of colors that can be differentiated
From: neilzero-ga on 02 Aug 2004 16:58 PDT
 
I'm suspicious that the method of calculating 20,000 is wrong, but I
like the number, which would provide a perfect match in most people's
opinion if the color spacing was selected carefully instead of
mathematically. IMHO
Subject: Re: Amount of colors that can be differentiated
From: uksearcher-ga on 03 Aug 2004 09:00 PDT
 
hi,

thanks for the below website which i am aware of. unfortunately it
only gives a very vague idea of how many colors we should be able to
differentiate but unfortunately there is no reference and a concrete,
scientifically proven result which i am looking for.

as for the other suggestion of a total of 20,000 i agree with the other comment.

but thanks for the effort
Subject: Re: Amount of colors that can be differentiated
From: stantheman-ga on 10 Aug 2004 07:07 PDT
 
There isn't one set answer to your question. Different people have
different ability to distinguish between colors and one person might
think two colors are identical while another person could see
differences, so there are many different answers to your question. One
possible answer would be to look at the way computers and digital
cameras generate color. Each pixel in a 24 bit computer generated
color has three coordinates: R, G and B. Each of these coordinates has
256 possible values ranging from 0 to 255. Therefore, the number of
colors for a pixel is 256 cubed (256 * 256 * 256) or approximately
1.678 million. This serves to produce an image that most people accept
as being a good color rendition of the original object, but some
people will see finer color differences than this.
Subject: Re: Amount of colors that can be differentiated
From: eye2eye-ga on 17 Aug 2004 18:56 PDT
 
I am a post grad researched in Ophthalmology with an optometric
background. Through the years I have had experience with clinical
testing and diagnosis of colour vision using various tests
anomaloscopes and feel I could throw in my 2 cents worth.
When commenting on colour, one must distinguish between hue and
saturation/luminosity. Hue can be defined as the appearance of a
single wavelength of light in photopic conditions(daylight, cone not
rod function). We must also include in this definition the large range
of non-spectral purples. Saturation is related to the amount of hue
present. Highly saturated hues are whitish or pastel(e.g. Pink),
whereas low saturations are string vivid hues(e.g. Red). As a
corollary, low luminosity colours appear blackish, high luminosity
again approaches the vivid colour.
Clinically we are not too interested in saturation/luminosity as this
does provide much detail as to the ability to percieve colour and
physiologically there are no great differences in photoreceptor
make-up to cause marked differences betwen individuals. Therefore, I
am not aware of any robust research which attempts to quanify
saturation/luminosity increments.
If your question is primarily regarding HUE...then I think I have your answer.
There is a clinical test called the Farnsworth 100 Hue test. This test
is founded on sound scientific, physiological and clinical knowledge.
The test is designed to detect observers who suffer from colour
confusion. Originally, the test consisted (arbitrarily) of 100
circular targets with colouring taken at discrete intervals from the
CIE chromatisity diagram i.e. the targets were designed to vary only
in hue. Basically you mix up all the colours and the subject has to
arrange them into a circular rainbow (on the CIE diagram if you change
only hue you will arrive back at exactly the same hue; this includes
the non-spectral purples). Room brightness, illumination colour
rendering, luminosity and saturation are all controlled and constant.
After applying the test for several years it was apparent that normal
observers were not doing so well, therefore, the test was reduced to
84 hues (but the name "100 Hue" remained.
In clinical practice we use JND increments, Just Noticable
Differences. It is deemed by the Farnsworth test that a normal
observer can distinguish 84 just noticable differences in hue.
If you are interested saturation effects you might have to conduct
your own research. Bear in mind though that if you consider the
dimmest target we can see, our eyes can adjust through 9 log units of
intensity i.e. we can still resolve detail on targets which are 1
billion times brighter!
I hope that this at least solves part of the puzzle.

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