Colours: primary & secondary
Don H
green, yellow, orange, red), then where do the following hues (ie.secondary
or intermediate), fit into a range of wavelengths - brown, purple, cyan,
magenta? Or, don't they have unique wavelengths?
Also, if white is presence of all colours, and black is total absence, then
is grey a mixture of black/white, rather than a "colour" in its own right?
=====================================
formerly known as 'cat arranger'
"Don H" <donlhu...@bigpond.com> wrote in message
news:hUvhd.6941$K7....@news-server.bigpond.net.au...
: If we take colours of a rainbow as primary or basic (violet, indigo, blue,
:
One thing I don't know is what colors have more than one frequency in them
and if there are any pure colors.
One thing I know is that there are two basic color models, if that is the
right
word. One is subtractive the other additive. Things like paint and printing
are
subtractive. When you mix colors the color gets darker.
The other additive is like a computer screen or television. When you add
colors
RGB (red green blue) you get lighter colors. 100% RGB is white. If you add
red paint and green and blue you'll get a darker murky color probably
something
like that.
Colors in the subtractive model are visible because of the light reflecting
and
absorbing properties of the surface. It may be that when you mix colors... I
should say it is not clear to me why it is that when you mix colors their
light
absorbing properties combine when it is just as easy to imagine that their
light
reflecting properties could combine.
This subject is interesting to me. Thanks for posting. Please follow up with
what you learn on your own.
: -)
Don H
Physics: Basic Facts" in which the additive and subtractive viewpoints are
illustrated as coloured triangles.
With adding, you end up with white; with subtraction you get black. But it
was when I tried to decide where exactly purple (red+blue) should go in a
spectrum, that I though maybe each hue has a unique wavelength (or composite
one) which would decide the issue.
When different coloured paints (eg.blue+yellow) are mixed, what actually
happens? Do the colours inter-react, or merely blend in some kind of
suspension, with the visual result (to us), of a fine patchwork of
individual colours which seem green? This seems to be case with grey,
because black and white are absolutes. Though to a completely colour-blind
mammal, the intervening colours between black and white, presumably appear
as various shades of grey.
Is blue wavelength actually "increased" by yellow, with result being
green, when paints are mixed? Or is it a mix of both original wavelengths
which hits our eyes, and our eyes can't differentiate?
I'm trying to get away from adding/subtracting, and interpret all in terms
of a basic spectrum, inter-reactions, and wavelengths - thus inserting the
intermediary colours/hues at appropriate places in the overall spectrum.
Some, like brown (red+yellow+a little black) are anomalous, but may be
below red. The colour code chart (ibid.pg 55) shows (for coding resistors):
(figure/colour) -
0 = black; 1 = brown; 2 = red; 3 = orange
4 = yellow; 5 = green; 6 = blue; 7 = violet
8 = grey; 9 = white.
- but this is a technical application of colours, for practical purposes,
and so not strictly scientific.
=================================
"formerly known as 'cat arranger'" <goodidea19...@hotmail.com> wrote
in message news:uuwhd.196105$a85.13633@fed1read04...
Craig Franck
> If we take colours of a rainbow as primary or basic (violet, indigo, blue,
> green, yellow, orange, red), then where do the following hues (ie.secondary
> or intermediate), fit into a range of wavelengths - brown, purple, cyan,
> magenta? Or, don't they have unique wavelengths?
Since we only have three color receptors (a tiny minority have four),
monochromatic (single wavelength) light -- like the RGB pixels in a
monitor -- would either be red, green, blue, or no color perceived.
Everything else is a mixture of these three colors. White to dark-gray
is a neutral color in that it is equal amounts of RGB. Black is little to
absolutely no white light.
The quality of colors we see is the result of cell receptors (rods, cones)
firing in the eyes, which then cause neurons to fire in the visual cortex.
IIRC, there is only one neurological response to red, green or blue; the
cell's response is the same across all wavelengths that it is capable of
detecting, like a scale that either says one pound or no weight.
However, due to a huge amount of processing by your visual cortex,
what you see and what hits your retina are quite distinct. Coal in the noon
sun is much brighter than snow in the shade, but snow looks white and
the coal black (color constancy).
It might seem curious why we see a continuous spectrum from sunlight.
It's because R-G-B are a continuous part of the spectrum. Yellow equals
red + green, so it blends smoothly between the two, with balances of less
than 50/50 on either side of pure yellow. Same for cyan with green + blue,
and magenta with red + blue.
This link shows exactly how this works:
http://www.rgbworld.com/color.html
--
Craig Franck
craig....@verizon.net
Cortland, NY
Keynes
wrote:
The brain processes colors in a relational mode rather than absolute.
There's a famous blue painting of a goldfish in a bowl, but the fish is actually
pink, not orange as it appears. Coal isn't really black when it reflects
a lot of light. Non painters call things this color or that, but painters
must see all the colors in a thing or else they are making a poster or
coloring book. Snow on the mountains is white in the sun and blue in the shade.
Leaves on a tree are white, black, and green, shifting with the wind.
The air has color. Things distant can fade to white or blue. At low light,
all color is washed out to greys. The magic of realistic painting is to put
aside the logical colors of things and to see the actual colors that are there
and copy them to the artwork.
Chickenlips
"Keynes" <Key...@earthlinkspam.net> wrote in message
news:ce7eo0pr71cu8vk78...@4ax.com...
Then there are those, like Immortalist, who see everything
as brown. Of course, there is a logical explanation for this
odd situation and it has nothing to do with the firing of
neurons.
>
>
>
>
Don H
portion of electro-magnetic waves is objective; merely waves.
What baffles me is: why there should be any trace of red at the blue end
of the spectrum?
Violet is bluish-purple, according to the dictionary, but purple is a
"colour between crimson and violet"; hence, red is there, even if diluted.
While violet waves are at opposite end of the spectrum from red waves,
maybe the eye/brain experience is more circular than linear - and portrayal
of a colour chart as circular has some relevance here.
When learning Art at primary school, we were shown a circle with three
diagonals, thus dividing the circle into six sectors. The primary colours
are entered: red, yellow, blue - with secondary colours between them:
orange, green, purple. Note that purple completes this circular
arrangement, linking red and blue. Perhaps our brain operates in similar
"circular" fashion - whatever objective reality might be re wave length?
=================================
Don H
colours to the human eye. The bandwidths of these are, in nanometers -
(Source: Collins Gem -"Physics: Basic Facts"):
Violet: 400-420
Indigo: 420-450
Blue: 450-500
Green: 500-560
Yellow: 560-600
Orange: 600-650
Red: 650-760
If we take each, and record its range, we get -
Violet: 20
Indigo: 30
Blue: 50
Green: 60
Yellow: 40
Orange: 50
Red: 110
Totalling these, we get 360 (or, full range: 760 minus 400), which, oddly
enough, is the number of degrees in a circle.
Artists, if they continue to use the traditional six-sectored circle with
red, yellow, and blue, as primary colours, usually have sectors of equal
dimensions; but, if we replace them with a proportional classification of
the seven colours (VIBGYOR), starting at geometric zero (East point of
compass), and proceeding anti-clockwise, the result is interesting.
It puts Yellow at 180 degrees; straddling that point, with 20 nanometers
of its bandwidth each side.
But Yellow is in the middle of the overall spectrum, if we take 400 + 180
= 580; because its range is 560 to 600. This is odd, because we might think
Green should have the honour, as there are three colours either side:
Violet-Indigo-Blue, and Yellow-Orange-Red. Perhaps this is equally valid,
and which view you adopt depends on your purpose.
For example, the "Additive" primary colours, as used with computer
monitors, is RGB (Red, Green, Blue), which allegedly add up to White (but
only if they cover full range of 400 to 760?).
On the other hand, the "Subtractive" primary colours, CMYK, used in
Printers and other paint-mixing, are: Cyan (greenish-blue?), Magenta
(red-violet?), and Yellow. Which, while they have the advantage of
including Yellow as a primary, when mixed don't completely give Black, but
"a muddy brown" (Source: EPSON printer manual), thus needing a black-ink (K)
supplement.
Those who were ready to concede Yellow as biased towards Red end of the
spectrum, may now have a case for claiming Red-Yellow-Blue to be primary;
indeed, artists may stubbornly insist on using them, for practical purposes
at least.
[ NB: the "mean" position of Yellow is confirmed by passing light through a
crown-glass/flint-glass prism combination, with flint-glass prism inverted
with respect to crown. "When..a beam of white light traverses the pair, the
extreme rays, red and blue, are deviated but the mean ray (yellow) is not."
Source: "Basic Physics: Light" by Martin & Connor; 1949. ]
======================================
"Don H" <donlhu...@bigpond.com> wrote in message
news:hUvhd.6941$K7....@news-server.bigpond.net.au...
Don H
them, via cones in the retina. Bees see ultra-violet; snakes detect
infra-red.
Why violet and indigo seem to have a red component is a mystery, but it's
here a circular presentation may be relevant. Perhaps our colour vision has
only a limited range of options, which, when exhausted, recommences?
If "purple" is blue+red, of which violet and indigo are hues (?), then
maybe "red" can be classified into scarlet (orange tendency), and crimson
(blue trend), with, say, vermillion, in the middle.
An interesting book on the whole topic of colour is - "Color Theory Made
Easy: A New Approach to Color Theory and How to Apply It To Mixing Paints"
by Jim Ames (Watson-Guptill Publications; NY: 1996), which is a
comprehensive and honest presentation, though it is possible to disagree
with the author's conclusions.news:GMxjd.25063$K7.1...@news-server.bigpond.net.au...
> The spectrum of "white" light from the Sun consists of seven distinct
Don H
appear bright bluish, the coldest red; while our Sun is a middle-aged star,
and yellow. Hence, blue (shortest wavelength= more energy?) is nearest to
"pure" white light, while red (longest wavelength=least energy) is nearest
black?
The solar spectrum has some ten thousand spectral lines, which indicates
missing elements, ie. due to absorption before reaching our eyes. This can
indicate what elements are present in the Sun, eg. sodium <- See: "Basic
Physics: Light" by Martin & Connor; 1949. ]
violet; strontium = red; barium = green....Why? Has this any relationship
to atomic structure of elements?news:rmQjd.28468$K7.2...@news-server.bigpond.net.au...
Don H
of grass."
Colour has three qualities - hue (predomination); saturation (purity), and
luminous intensity (power).
But any colour which reaches the human eye, irrespective of source, must
be definable in terms of electromagnetic wave-length; whereby those
secondary colours of, say, red - scarlet, vermilion, and crimson - could be
allocated a numeric denoting wave-length(s) involved. If this is possible,
then the arbitrary numbers currently allocated to all the various colours in
art could be objectively and universally described.news:rmQjd.28468$K7.2...@news-server.bigpond.net.au...
> Wave-lengths are objective facts; colours rather subjective, as our eyes
see
Don H
The Color Wheel Company,
which sells three basic colour wheels:
1) Color Wheel (red-blue-yellow)
2) the Web Wheel (RGB)
3) CMY Primary Mixing Wheel
See>> http://www.colorwheelco.com
Web-safe colours are based on RGB, using hexadecimal combinations:
00 33 66 99 CC FF which translate as R/G/B -
00 051 102 153 204 255, or, as percentages -
0 20 40 60 80 100.
These colour wheels should be available from any good local artist-supply
dealer.
=================================news:2x6nd.41146$K7.1...@news-server.bigpond.net.au...
Don H
a "bleaching effect of light on a pigment (rhodopsin or visual purple)".
Yes, Purple is, perhaps, of significance. It is the one colour which
doesn't fit in between the two spectral extremes of Red and Blue, but is a
combination of them - for which we normally give a circular presentation of
all colours, not linear (spectrum). But Violet is a hue of Purple?
If Purple is THE primary (composite) colour, then the two secondary
(component) colours are Red and Blue, between which you can choose Green or
Yellow as next in (derivative) significance.
Another aspect: the contention that derivation of some colours is
"additive" (from lights), but in other case is "subtractive" (paint
pigments), seems a bit odd. In both cases, colours are superimposed,
blended, or mixed, and hence "additive", but in the former we are dealing
with light through a gaseous medium, while in the latter, it is through a
liquid-solid medium. Might not this be of significance? In both cases,
White should be the expected result of addition (if all colours are
present), but Black tends to result from paints, due to much greater opacity
of the medium? (In both cases, absorption occurs.)
===================================news:57rod.45052$K7....@news-server.bigpond.net.au...
Keynes
Light radiates. Paints only reflect.
Sylvia Else
Thing is, these colours don't really exist in nature. All there is is
radiation at various frequencies and intensities. Any given source of
light (emitted or reflected) is producing radiation at multiple
frequencies and insensities.
The distinct colours only exist in our brains, as a result of the
particular sensors we use in our eyes.
Sylvia.
formerly known as 'cat arranger'
: On Tue, 23 Nov 2004 19:43:14 GMT, "Don H" <donlhu...@bigpond.com>
Paint or pigment reflects and absorbs.
But you are essentially correct.
formerly known as 'cat arranger'
: Colour vision, according to The New Penguin Dictionary of Science, is due
: > >
: >
: >
:
:
You seem to be trying to cloud the issue. Creating confusion.
Why?
formerly known as 'cat arranger'
"Sylvia Else" <syl...@not.at.this.address> wrote in message
news:41A3BA02...@not.at.this.address...
:
:
Color only matters to us because of its creation by our
brains and the sense of sight. It is still important and in the
realm of things like color it doesn't matter that it doesn't
exist in reality, as you choose to express it. Nothing exists
in reality without humans to see it. At least no human
existence, ie life as we know it does not exist without humans.
Phred
>"Sylvia Else" <syl...@not.at.this.address> wrote in message
>news:41A3BA02...@not.at.this.address...
>:
>: radiation at various frequencies and intensities. Any given source of
>: light (emitted or reflected) is producing radiation at multiple
>: frequencies and insensities.
>:
>: The distinct colours only exist in our brains, as a result of the
>: particular sensors we use in our eyes.
>
>brains and the sense of sight. It is still important and in the
>realm of things like color it doesn't matter that it doesn't
>exist in reality, as you choose to express it. Nothing exists
>in reality without humans to see it. At least no human
>existence, ie life as we know it does not exist without humans.
Perhaps as *we* know it, but ISTM there is enough intelligence in many
other life forms for "reality" to exist without us.
But this did remind me of that humorous old Berkeley limerick "God in
the Quad", e.g. this version attributed to Monsignor Ronald Knox:
<quoting>
There once was a man who said, “God
Must think it exceedingly odd
If He finds that this tree
Continues to be
When there’s no one about in the Quad.”
“Dear Sir:
Your astonishment’s odd:
I am always about in the Quad
And that’s why the tree
Will continue to be,
Since observed by,
Yours faithfully,
God.”
</quoting>
Incidentally, there's a neat little essay on body-mind dualism at:
<http://www.whitworth.
edu/academic/Department/Core/Classes/CO250/Readings/body.htm>
Cheers, Phred.
--
ppnerk...@THISyahoo.com.INVALID
Don H
be questioned. I'm thus raising some new aspects - which may be entirely
wrong, of course.
If you pass light through sequential coloured filters, how does this
really differ from mixing paints? - the resultant light is what matters. In
both cases some absorption or blocking occurs. If the filters are really
thick, then less light emerges.
If you add Red + Green/Yellow + Blue the result should be White (if it
spans the full spectrum), irrespective of how this is done.in message news:o8Pod.340279$a85.4460@fed1read04...
> :
> ...........
Don H
To doubt His existence? Absurd!
But when Faithful do pray,
Traffic is all one way.
Silence is all anyone's heard.
Those few who have "heard" a response,
Are deemed quite astray in the bonce.
To madhouse confined,
Or faithful to mind.
As for me, I'll take myself honce.
================================
"Phred" <ppnerkDE...@yahoo.com> wrote in message
news:30i2s2F...@uni-berlin.de...
Don H
of Grey, as follows: (hexadecimal / RGB).
FFFFFF / R255 G255 B255 (white)
CCCCCC / R204 G204 B204 (lighter grey)
999999 / R153 G153 B153 (light grey)
666666 / R102 G102 B102 (dark grey)
333333 / R051 G051 B051 (darker grey)
000000 / R000 G000 B000 (black)
This is how humans see greys, but apart the primates, most mammals are
colour-blind; to whom colours appear as shades of grey.
Birds, bees, octopus, can see colours.
The ability must have evolutionary benefit.
* The Color Wheel Company, Oregon, USA.
(Americans spell grey as gray.)
================================in message news:ucPod.340281$a85.128215@fed1read04...
block
> Birds, bees, octopus, can see colours.
Man must have spent a great deal of time and money discovering that the
octopus is the only sea creature that can see in colour - I wonder to what
end. Rather like the billions that were spent on getting the right
viscosity for tomato ketchup.
Sylvia Else
Filters subtract light - they only pass some of it. If one filter
substracts some of the light, and the next filter subtracts the rest,
then you're left with nothing - black. Paints behave the same way.
Why would you expect the result to be white?
Or was yours another of those deliberately obtuse troll postings I have
so much trouble with?
Sylvia.
Don H
The RGB system of "additive" colours is used in computer monitors, with
tiny phosphor dots.
I assume these dots are grouped in triad clusters of red, green, blue,
within each pixel.
The important aspect here is: they are not (?)superimposed, but
side-by-side. Thus they differ from pigments (or filters) which are
superimposed, or mixed - which diminishes light, due to opacity, and/or
progressive absorption.
In the case of a computer monitor, while the degree of red / green / blue
varies with hue, each is separately transmitted to the human eye, which "can
be fooled - the color of any wavelength can be simulated by mixing light of
other wavelengths" (see book: Dictionary of Computer and Internet Terms by
Dowining, Covington; Barron's). Hence, I suppose, the red-green-blue
combination reaches our eyes as a merged colour, but undiminished in
intensity.
If a similar test was applied to pigments, eg. by creating a colour wheel
of equal red-green-blue sectors, and spinning it - the result should be
white, or at least a light grey? i.e the colours are separately blended,
not mixed in a pot. Opacity or mutual absorption is then not a factor.
Incidentally, MS FrontPage Express gives a full menu display, showing
details of a selected colour: proportions of R-G-B, with Hue, Saturation,
Luminosity; the decimal values can be converted to hex using Calculator (in
Scientific mode).
===============================
"Sylvia Else" <syl...@not.at.this.address> wrote in message
Don H
yet untested.
We can assume any species which has a coloured skin probably has colour
vision, especially if the colour relates to mating courtship display. (Most
mammals are drab) Some frogs use vivid coloration as warning, to predators,
of poison glands - but does this mean frogs themselves see colours?
Certainly it implies most predators can.
===============================
"block" <bl...@here.com> wrote in message
news:B55pd.166$i26...@newsfe3-gui.ntli.net...
Sylvia Else
Is there still a question here, or does that resolve it?
Sylvia.
formerly known as 'cat arranger'
In the realm of subtractive color though is print media.
The color does not mix. The dots are pure cyan, magenta,
yellow, and black. So the perceived colors are actually
combinations of subtractive colors positioned in a way
that their light reflection is additive. If that sounds like I'm
trying to be confusing, I'm not, really.
"Don H" <donlhu...@bigpond.com> wrote in message
news:boqpd.48272$K7.4...@news-server.bigpond.net.au...
: Sorry, I must've chosen wrong example; didn't actually check it out.
: >
: >
: >
: >
: >
: >
: >
: >
:
:
Don H
(eg. blue and yellow) what really happens? Do they chemically react to form
a resultant colour? Or is it a physical mix, a blend, in suspension, of the
two? Then, the two colours hit our eyes, and the two wave-lengths, one
shorter than the other, produce a net effect?
I re-viewed George Pal's "The War of the Worlds", in which the Martians
allegedly have "three distinct pupils" (R-G-B), "like a TV camera"; the
resultant image being "white".
RGB are the chosen colours for TVs and computer monitors; CMYK for
printers. Yet any combination which covered the light spectrum could be
used - RYB in both cases, for example. Why the disparity between monitors
and printers? historical evolution? (By making them the same, there'd be no
need for "calibration".)
Cyan (greenish-blue), Magenta (red-violet), and Yellow, don't quite cover
the spectrum, hence need to include Black.
================================in message news:dnupd.356306$a85.307898@fed1read04...
>
> In the realm of subtractive color though is print media.
> The color does not mix. The dots are pure cyan, magenta,
> yellow, and black. So the perceived colors are actually
> combinations of subtractive colors positioned in a way
> that their light reflection is additive. If that sounds like I'm
> trying to be confusing, I'm not, really.
>
Sylvia Else
Don H wrote:
> I get what you mean. Even when mixing two different paint colours together
> (eg. blue and yellow) what really happens? Do they chemically react to form
> a resultant colour? Or is it a physical mix, a blend, in suspension, of the
> two? Then, the two colours hit our eyes, and the two wave-lengths, one
> shorter than the other, produce a net effect?
> I re-viewed George Pal's "The War of the Worlds", in which the Martians
> allegedly have "three distinct pupils" (R-G-B), "like a TV camera"; the
> resultant image being "white".
> RGB are the chosen colours for TVs and computer monitors; CMYK for
> printers. Yet any combination which covered the light spectrum could be
> used - RYB in both cases, for example. Why the disparity between monitors
> and printers? historical evolution? (By making them the same, there'd be no
> need for "calibration".)
> Cyan (greenish-blue), Magenta (red-violet), and Yellow, don't quite cover
> the spectrum, hence need to include Black.
They're both trying to do the same thing, which is to stimulate the
three types of colour receptive in the eye to produce the same effect
that a particular frequency or combination of frequencies would. These
receptors are sensitive to three bands of the spectrum, roughly centred
on red, green and blue light.
However, monitors and printers have different starting points.
In the case of a monitor, the starting point is black - there is no
light emitted from the screen, except from the illuminated dots, so the
strategy is to add light by illuminating dots in the red, green and blue
parts of the spectrum.
In the case of printers, the starting point is an assumption that the
paper is illuminated by white light, so the strategy is to absorb areas
of the spectrum, leaving only those parts required to stimulate the
desired receptors.
Cyan will absorb light in the red band, magenta will aborb it in the
green band, and yellow will absorb it in the blue band. When you mix two
of these together light will be absorbed by both of them, so the
reflected light is what is absorbed by neither.
In theory this would mean that black could be produced by mixing all
three, but the absorbtion characterstics are not perfect, and inks are
expensive anyway, so it makes sense to have a black pigment (absorbs the
entire visible spectrum).
One could envisage a printer that used black paper, and which sprayed
red, green and blue pigments onto it, in a patter similar to that used
by a monitor. However, the result would be something that looked rather
dark because most of the light falling on it would be absorbed. You
could view it in very bright light - but this is hardly practical.
Sylvia.
Sylvia Else
BTW, sorry about the 'obtuse troll' comment - I've been keeping some bad
company in other NGs :(
Sylvia.
formerly known as 'cat arranger'
The amount of color displayed by differnet things, ie monitors,
print, paint, others are different. Each has colors that the others
can not present, I think. And some have greater ranges.
"Don H" <donlhu...@bigpond.com> wrote in message
news:a0Kpd.49431$K7.3...@news-server.bigpond.net.au...
:I get what you mean. Even when mixing two different paint colours together
:
:
formerly known as 'cat arranger'
Oh yeah, and the main thing is that if you look closely at
color in a magazine picture, you'll see that the colors don't
mix at all. Each color is separate and it is the pattern of the
colors, sometimes the size of the dots of color, and their
placement, and possible other things, that creates the perception
of color.
"formerly known as 'cat arranger'" <goodidea19...@hotmail.com> wrote
in message news:5kVpd.360574$a85.355683@fed1read04...
:
: The amount of color displayed by differnet things, ie monitors,
::
:
:
formerly known as 'cat arranger'
"Sylvia Else" <syl...@not.at.this.address> wrote in message
:
:
The amount of ink put on paper is another issue. If you didn't do what
is called 'black replacement', I think, which means replacing combinations
of C, M, and Y with black in the right proportion, then the paper would
have so much ink on it that it wouldn't dry in time to be stacked, or maybe
the paper would wrinkle.
Ink printed on black paper would have to have a lot of pigment to cover
the black. I don't think it is practical and I've never seen anything
printed
on black paper except for spot color which is just one color that is not
intended to be mixed. An example would be silver or gold paint on a
black page.
Don H
power is on. That, and colour of paper in a printer, are somewhat
irrelevant, because any colour is lighter than black and also darker than
white.
I assume power input into either device is virtually constant, and so,
when a program in eg. HTML designates a colour in hexadecimal or equivalent,
it is instructing computer to maximise or reduce output re a constant
phosphor dot colour hue (R,G or B). How is this done? Is it by reducing
size of respective dot, or reducing its overall contributing illumination?
If latter is so, why not make ALL phosphor dots white, and do the same
thing? 'cos all colours are of some wave-length less than white. But would
this work for browns or greys? Not all colours are pure, and located along
the light spectrum, but are all made of wave-lengths, of whatever mixture.
If a typical brown is hex = CC9900, then this is a mixture of red and green
(no blue) under current system, and translatable into a spectral equivalent,
I assume, by "letting through" only those selected aspects from a white
phosphor dot source. By reducing current triad of colours (RGB) to a
variant of one (white), definition might improve; indeed, dots could be
almost eliminated.
Same applies to printers, with CMYK, but here we are dealing with
pigments, so, while the principle might be the same, the technique must
adapt. Presumably a white pigment can't have its output wave-length altered
by any physical, electronic, or progammed means, to produce a colour? But
if such pigment is made by mixing primary colours (even if appearing
black?), then same query applies. But once mixed, they can't be "un-mixed"?
It is interesting to read in books on the art of painting, how much fuss
is made about cyan and magenta, to differentiate them from blue and red, yet
yellow is casually accepted as a known, in spite of it having as wide a
range of hues as the other two. So which yellow are we referring to?
================================
"Sylvia Else" <syl...@not.at.this.address> wrote in message
formerly known as 'cat arranger'
You bring up an interesting question. You would think by looking
at a light spectrum chart that you could generate any color by varying
the frequency or amplitude or something, which should be able to be
done by varying the electricity to a single diode. But we use 3 diodes...
And you see a red radiation as really the exclusion of other radiations.
That's interesting. But the difference between what happens when you
combine two light sources and when you mix two pigments. But the
printing process is more like the monitor source, in a way, because the
CMYK (cyan magenta yellow black - k is used for black to make sure
B for black isn't confused with blue, I've been told) ... the colors of
printing aren't mixed but positioned next to each other.
So I'm wondering if you position small dots of cyan next to small dots of
magenta, do you get an additive effect or a subtractive effect? If you take
a color wheel and spin it, there is an additive effect, which seems to
indicate
that the same would be true in the printing process... but I don't think
that
is true... ?
So which colors are pure and which are combinations of two or more
light frequencies?
"Don H" <donlhu...@bigpond.com> wrote in message
news:tx3qd.50532$K7.4...@news-server.bigpond.net.au...
:A TV or computer monitor screen is black - but is blue, or whatever, when
: >
:
:
Don H
light spectrum. When we try approximating to white, or black, by using
three colours, RGB or CMY, we fall short - unless these are somehow made to
span the full spectrum.
With CMY, compensation is by adding Black, but even RGB is not fully
equivalent, as its Yellow, produced by R+G (hex=FFFF00) would require
spectral Yellow to have Blue added, to fully match.
When a combination of, say, Blue + Yellow wavelengths hit our eyes
(giving Green effect), I suppose some "cancelling out" process is involved,
whereby shorter Blue wavelengths (450-500) are "extended" in length by
longer Yellow (560-600), to give net result - of the intermediate, Green
(500-560) - or so it appears to us. But if any "pure" colour alone is
transmitted, and seen, then no problem.
If an electro-magnetic wave in 500-560 range is generated, by whatever
means, we see Green.in message news:WM4qd.360635$a85.342690@fed1read04...
Don H
colour vision develop, and in what way?
Existence of colour-blindness in humans may be a key, as a recessive gene
is involved, and there can be inability to distinguish, eg. blue from green,
or green from red, especially in males.
Yellow is the light-est (sic) of colours, and maybe it was the first
colour experienced by humans - or it might have been the last.
If a colourless spectrum of white, shades of grey, and black, was the
original pattern, then subsequently: a yellowish white to a purplish black,
may have been accompanied by reddish-orange and greenish-blue. That is,
reverse of our normal spectral analysis of "primary" and "secondary"colours.
Ability to distinguish red from orange, and green from blue, may have come
later. Unless full spectral analysis capacity suddenly sprang into
existence, from initial white-grey-black vision.
====================================
Don H
================================
"Chlorophyll absorbs its energy from the Violet-Blue and Reddish orange-Red
wavelengths, and little from the intermediate (Green-Yellow-Orange)
wavelengths." - (see: www.emc.maricopa.edu)
This is explained, in the article, by sea origin of plants, whereby
shorter wavelengths don't penetrate much below 5 metres deep, so ability to
absorb energy from longer wavelengths might have been an advantage for algae
at lower depths.
But why the gap in the spectrum, whereby the intermediate wavelengths are
of less relevance? Because algae/seaweed doesn't occur at intermediate
depths?
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