Re: Viewer perception of neutral gray
Re: Viewer perception of neutral gray
- Subject: Re: Viewer perception of neutral gray
- From: Terry Wyse <email@hidden>
- Date: Wed, 5 Sep 2007 08:14:06 -0400
Bob, et al,
And here I thought I was just getting "better" at this color
management thing over the years (proofs are matching better, press
sheets are matching better, etc.) but it could be that my eyes are
becoming duller with age so I only THINK things are improving.
On the other hand, I did take the Farnsworth-Munsell 100 Hue Test a
couple of months back and only missed one so I'm hoping that my eyes
are still good enough to keep doing my job.
research shows that some women (2-3% ?) have four types of cone
(tetrachromats) like many birds, ampibians, and reptiles.
Thanks for that. I've got a few things to tell my wife and I don't
think she'll be all that happy about it ("yes dear, you might see
color better than me but you're still a snake!").
I'll let you know how that goes over with the misses.
Thanks,
Terry Wyse
On Sep 5, 2007, at 5:11 AM, Bob Frost wrote:
Mark,
1. People have 3 types of color receptors in their eyes,
At the very least, you need to put the word 'most' at the beginning
of your sentence, since it has long been known that some people
only have two types (dichromats), and some only have one type
(monochromats) - 8% of men and 1% of women are partially or
completely color blind.
In addition, recent research shows that some women (2-3% ?) have
four types of cone (tetrachromats) like many birds, ampibians, and
reptiles. And from these results, about 99 million women in the
world could have this four-color vision. The extra cone has
pigments between the red and green.
Here's a quote from a research paper out of UC, San Diego, by
Jameson et al.
in 2001
http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?
cmd=Retrieve&db=PubMed&list_uids=11495112&dopt=Abstract
"We use genetic analyses to examine an important position in the gene
sequence, and we empirically assess and compare the color
perception of
individuals possessing more than three retinal photopigment genes
with those
possessing fewer retinal photopigment genes. Women with four-
photopigment
genotypes are found to perceive significantly more chromatic
appearances in
comparison with either male or female trichromat controls. We
provide a
rationale for this previously undetected finding and discuss
implications
for theories of color perception and gender differences in color
behavior."
There is also other research suggesting that we all are all
tetrachromats - and that our UV receptors are blocked by the
absorbtion of UV in the cornea and lens - http://www.
4colorvision.com/files/tetrachromat.htm.
So the women with the extra receptor may actually be pentachromats,
like the lowly pigeon!
often known as alpha, beta and gamma.
Or more correctly as L, M, and S (long, middle, and short
wavelength-sensitive); Photopsins I, II, and III; Protan, Deutan,
and Tritan; or erythrolabe, chlorolabe, and cyanolabe.
2. Each type of receptor very roughly corresponds to red, green
and blue.
There are other reseach papers showing that there is considerable
genetic
variation in the pigments in two of our three cones, which cause
variation
in our color perception.
<http://www.ncbi.nlm.nih.gov/sites/entrez?
Db=PubMed&Cmd=ShowDetailView&TermToSearch=10708034&ordinalpos=1&itool=
EntrezSystem2.PEntrez.Pubmed.Pubmed_ResultsPanel.Pubmed_RVAbstractPlus
>
5. Since we know that "color blind" people exist, it is very
unlikely that
most people have equivalent spectral response.
Another variation in color response that is often ignored, is due
to the changes in the color transmission of the lens with age. Here
are some results from a replacement lens manufacturer
showing the difference in color transmission of a 25yr-old human
lens and a
54yr-old lens:
wavelength 450 500 550 600
650 700
25yr-old 35% 70% 75% 75% 75% 75%
54yr-old 25% 45% 50% 55%
57.5% 60%
Reduction 29% 36% 33% 26% 23%
20%
As you can clearly see the older lens has 20% reduced red
transmission, but
this progressively increases across the spectrum to 36% in the
blue. And
this difference is found at a mere 54 yrs of age! It is much
greater at 60,
70, and 80.
Last year I had both lenses replaced as they were going cloudy and
affecting my resolution, but with 3 months between the ops. So I
had three months with one old lens and one new one - qhite
interesting!
As soon as I came out of the op theatre, even though my sight
through the new lens was initially blurred, the difference in color
was
amazing (it is the first thing most who have lens replacements
comment on
apparently). The nurses shirts were blue instead of a gray-blue, a
cyan
poster on the wall was blue, the sky was much bluer than with my
old eye,
and a pink skirt that looked quite a nice color with my old eye was
quite
lurid with the new one!
Next day the blurring had gone, and I could now see things on the
horizon as
sharp as I ever could, and having just walked aroung our village,
it's like
one eye is seeing things in 5000K and the other in 6500K. Using both
together seemed to use an intermediate 'WB' at first, although
later the new lens began to dominate.
I tried a rough measurement of the difference in my eyes using
Photokit
Color in CS2, and the difference was something like a .15CC yellow
filter.
As yellowing affects all those over about 50 yrs, there are an
awful lot of
people out there in the world who don't see as much blue as they
did when
they were young.
So perhaps publishers of color management books should issue buyers
with a
set of blue graduated filters. If you are 50-60 view the pictures with
filter 1, 60-70 use filter 2, 70-80 use filter 3. ;)
To end with, here is a nice quote from an essay on tetrachromacy -
"A recent paper by Kimberly Jameson, Susan Highnote and Linda
Wasserman of the University of California, San Diego, concerning
females who may have tetrachromacy shows amazing results. Up to 50
per cent of women are tetrachromatic and can use their extra
pigments in "contextually rich viewing circumstances". For example
when looking at a rainbow, tetrachromat females can segment it
into, on average, 10 different colours, whereas their trichromat
brothers and sisters can see only seven, much as Isaac Newton's
red, orange, yellow, green, blue, indigo and violet. Consequently
for those special tetrachromat women, this island that they inhabit
may be seen in emerald, jade, verdant, olive, lime, bottle and 34
other shades of green. Apparently, men and women do see the world
differently."
http://www.science-writer.co.uk/award_winners/16-19_years/2004/
winner.html
'Normal' human vision? 'Standard Observer'? Most of us are
different!!
Bob Frost.
----- Original Message ----- From: "Mark Rice" <email@hidden>
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