Colour and Color TV, Vibration and Sound, Program and making

Color and its composite

I have to claim at first, the picture left is drawed by me arbitarily at MSpaint software. only for reference.

and We discuss here only relate to add color method. If you work in printing and painting field, that you will use substration method.

Great Newton told us that the light of the sun is composed of seven color light.

That is red, oringe, yellow, green, cyan, blue and magenta. This is the principle what we'd known since we were childhood. (I seem to show off myself )

Lets continue...

Thomas Young explained at his experiment in 1802 that the light is made up by main three principle color, which stimulated our eye then make us sense light and verious colors. Further more, Helmholtz described their quantity relationship to form the basic theory of three principle color.
I remember I read an old book which discribed it in theory of ether, haha, we know its wrong. because people at the time hadnt known field theory yet. Today we know its explained by theory of field.
However, from that time on, we begine to implement our color picture by these three elements color. and this is also the basic of our modern color TV set as well as pringting industry.
Today the chromatics has developped very fast and play an important role in our life.

Lets see the equation,

k*R + m*G + n*B = Color (countless magneficant beautiful color) .......(1)

where coeficient k,m,n can be [0,1]

when they are 1, we get

R+G+B=W

and

R+G= yellow

G+B=cyan

B+R=magenta

This is our above picture.

From equation 1, we see, if we use A/D converter and quatitization coeficient value is 8, just like our computer, using multication, we can get

2^3x8 =? 64M (where M=1024)

wow, countless color we get!

Thats why we often say my computer can display 64M colors.

To this moment, we shall ask do you know what white color is?

How many kinds of wilte color do we have ?

There was a wrong that have to correct as follow.

where M = 1024x1024.

if the advanced set adopt 12 bit encode, the color will be as many as 2^3x12= 4G

wow, countless colors appear in front of you.

Colour is a phenomenon related to the eye's sensitivity to certain wavelengths/frequencies of electromagnetic radiation. In the case of image processing, additive colours can be obtained by varying the amounts of red, green and blue in the incoming light, so as to stimulate the three receptors in the eye that are sensitive to these colours. The brain interprets the amplitude of these three colours relative to each other to produce nearly all the colour sensations, and in this way only mixtures of red, green and blue light are needed to render these colours in an understandable image.

A television image adds together the various intensities of red, green and blue to produce a tiny multi-colour patch on the screen. Because of its small size in terms of the square angle relative to the point of focus in the eye, the brain cannot resolve the three colour dots individually, and instead resolves a colour that is an amalgam of the intensities of the three dots as though the colour was coming from one place on the screen. The image "tricks" the brain into seeing a single point of varying colour, whereas on a small scale the image is really a local matrix of three dots of colour of varying intensities.

yes, thats so called resolution of our eyes.

it depends on frequency and diameter of pupil. the high frequency the more large resolution we could get.

the arrangment of the dot on screen is either column line or triangle shape. when they were bombed by different intensity electric beam they give out different mixing light(color). some displayer is arranged in square, like LED large screen etc. for example 1:2:1 etc.

Since the issue of resolution has come up, and resolution depends on WAVELENGTH, not COLOR, this would be a good time to point out that this discussion seems to be ignoring the important distinction between ACTUAL COLOR and PERCEIVED COLOR. Red light and green light do not interact to MAKE yellow light, they merely fool the eye/brain into thinking yellow light is present.

I'm not sure of the exact wavelengths and bandwidths for the red and green phosphors in TVs, but lets just pretend for purposes of keeping things simple that the bandwidths are extremely narrow, that red is 650 nm and green is 550 nm. Mixing these two wavlengths together does not produce light at 600 nm (orangish yellow). A spectrometer measuring the output of the TV would show that no 600 nm light was actually present, only 650 and 550. But a spectrometer can discern an almost infinite number of wavelengths, while th eye can only discern three. The human eye/brain would assume that the light was yellow, because both the red and green sensitive retinal cells were being stimulated, and that is what yellow does.

Therefore if you wanted to calculate resolution of yellow objects on a TV, it would be based on the red and green wavelengths, not the perceived yellow. You should consider however that the retina has lots of cells for detecting light and dark (rods), and relatively few for detecting color (cones). As a result, while the eye may have the ability to resolve dark and light patterns with a resolution of about 30 cycles per degree, the ability to resolve patterns of color is much lower.

What happens on your retina is much like what happens in a child's coloring book. The printed black lines on the page are fairly clear. The child colors it in, but doesn't always stay 'within the lines' with the colors. The same thing is happening on your retina, but over time your brain has noticed this and has learned to put the colors back 'inside the lines'.

Johnfoti,

I am sleepy and need to nap but could not resist one comment.

As I understand it the brain is not tricked. It indeed sees the beat frequency resultant of mixing colors or frequency of the primary colors and that is what it knows as the various colors of the spectrum.

What has not been clearly stated is that visible light is a phenomenon of a range of electromagnetic frequencies. When you beat, i.e., mix two colors together you in fact get a measurable electromagnetic resultant, i.e, primaries blue and yellow result in a given frequency, green.

It is no different than in the radio frequency ranges of the electromagnetic spectrum where tuning in certain applications is the result of "beating" two frequencies against each other.

As I said I am sleepy and can't at the moment go deeper; I can't think that hard right now. Nonetheless, this business of color, as I suspect you would agree, starts with an understanding of the electromagnetic spectrum, of which visible light, as well as invisible ultraviolet and infrared, are a part and as well any beat frequencies occurring and limited to those ranges in which we have not given them derivative names like brown, violet, etc., because we don't see them as part of our everyday environment but nonetheless exist.

Furthermore, in the invisible range there are similar unnamed resultant colors such as those in the visible range which upon perceiving we give names like reddish, brownish, greenish, etc.

Another thing not yet mentioned here, although I expect someone with far more knowledge than I will chime in and offer a far more complete explanation, is the fact that our eyes in fact have parts, is it the rods or the cones, with dyes of the primary colors, hence color filters.

j.

Hi Jack,

I think the problem with this is that the beat frequency produced by two relatively close frequencies, such as the red and green, would not be some intermediate frequency, but some considerably lower frequency, somewhere out in the near IR. I don't have time to do the math right now, but there is a good discussion of this on Wikipedia, the first for acoustics, the second for light.

http://en.wikipedia.org/wiki/Beat_(acoustics)

http://en.wikipedia.org/wiki/Frequency_comb

Hi,

you put forward a interesting question. as we all know from college textbook that movement is incoherent and they will transport along their path individually. for example two waves transport forward according to their own path, but why we can hear a socalled beat frequency sound? thats becase of our ear structure.

our ear has a nonlinear response to audio vibration wave. so that we can hear that beat frequency. i.e the difference frequency between the two waves. If our ear has linear hearing, we couldnt hear the beat frequency but only two different wave theirself.

we can use this phenomena to tune our music instrument. Have you ever made it or seen it?

Back to color, if you test the two or three color with gauge, your can get the original color individually. but they act our eye, we can sense countless color on the screen.

this will concern to our eye cells, you can refer to relative book. in fact its out of my depth for most of them.

Lets continue to reply professor shyam's question, how tv set playbacks tremendous numbers of color accurately.

On the subject of beat frequencies, I think that air itself is a nonlinear medium, so the beat frequency is not a function of the hearing method (ear) but is in fact physically present in the medium. I worked as a musician for many years, and before the advent of those nifty electronic tuners, using harmonics and beat frequencies was the best method of tuning available, unless you were lucky enough to have perfect pitch.

To understand color vision, and the specifics of how a TV can fool the eye into perceiving a wide range of colors, it is instructive to consider the differences between how the ear and the eye work. In the ear there are many thousands of sensors (hairs) in each cochlea, each tuned to a specific frequency. We have so many that we can detect several different frequencies in the spaces between the conventional musical notes. Thats how we can tell if the violinist is playing a little 'sharp' or 'flat', and also how we can appreciated the beauty of the great continuous 'bending' of notes on a pedal steel guitar.

As has been mentioned, the eye (while vastly more useful to us in terms of gathering information about our surroundings) is much more limited, having only three frequency sensors. I remember seeing a graph several years ago of the actual response curves of the 'red', 'green', and 'blue' sensors, and being struck by the fact that for the most part all three types overlapped. The one we call 'red' had only slightly better response to red light than the 'green', and only slightly poorer response to the shorter wavelengths. From looking at this graph it becomes clear that when we see the red light from say an HeNe laser at 633 nm, that all three types of sensors respond, but in varying degrees. For us to unambiguously determine that the color is red means that we must have 'inhibitory' neural circuits, both in the retina and in the brain, that suppress the signals from the 'green' and 'blue' sensors.

Back to the color TV question. I think it is debatable that a color TV can 'accurately' reproduce the great range of colors in the visible spectrum, but that in fact what it does is 'precisely' reproduce the colors in a limited portion of the spectrum. I know that if I look through a narrow band 670 nm (deep red) filter that I can see a considerable amount of very red light. This is a color beyond the range of the conventional red phosphors in a TV. Likewise when I look at a rainbow, I can clearly see the violet light beyond the blue, but this is also beyond any of the conventional blue phosphors used in a TV. So what we get is a compressed color range, in which deep red and deep violet can only be suggested.

We see 'deep red' because the red sensors are stimulated, the green is stimulated but to a lesser degree, and the blue sensor is just barely stimulated. In this sense it is the absence of stimulation in the blue sensors rather than the presence of stimulation in the red sensors that is determinative.

So as I see it, the trick to precisely reproducing colors on a TV is a question of (1) precisely matching the filters for each color channel in the camera to the colors of their respective phosphors, (2) having enough dynamic range in each color channel in the camera to provide the detailed 'recipe' needed to produce the corresponding color on the screen, and (3) having enough dynamic range in each color channel on the TV to reproduce this recipe faithfully.

It should also be noted that the ability of the eye/brain system to adjust to very low light levels, and even to 'colored' light sources is significant. We can tell that a rose is red, even if the lighting is very dim or shifted towards the blue. This ability allows us to fool ourselves into seeing the colors on the TV as being 'realistic', even though the spectral and dynamic ranges are significantly limited compared to the original scene viewed by the camera lens.

If we want to accurately reproduce colors on a TV we will need to use at least four colors so as to include the far edges of the spectrum, the deep red and the violet.

Johnfoti,

"On the subject of beat frequencies, I think that air itself is a nonlinear medium, so the beat frequency is not a function of the hearing method (ear) but is in fact physically present in the medium."

It has been a long time since I looked in detail at issues of vision or hearing. On color vision you brought me up short. I may be in error and the source of it may have been in equating the manner of transmission of sound, mechanical vibrations of air molecules, as opposed to light, electromagnetic waves, which we variously talk of as photons, or waves, which straight on leads into a so-called mystery, i.e., the evidence of quantum effects demonstrated by the Young two slit experiment.

Nonetheless, if I understand you properly, in the above statement you are separating the ears mechanical function, i.e., transducing the mechanical vibrations of air that strike our ear as what subjectively we know as sound, into the electrochemical signals our brain "hears," from the mechanical form of transmission of that sound through air.

I don't really think you mean to do that. I doubt that you would argue that the vibrations in the ear, picked up and transduced by hairs in the cochlea, are not the same as the vibrations in air before it gets to the ear.

I think you mean to say that the physical vibrations of sound in the air are directly converted, through vibration of those hairs into electrochemical signal transmissions in our nerves and brain.

My problem, our problem with light, is that although we speak of it as individual photons, we seem to also speak of it as waves, leading to what I think is a confusion. What I think we should be saying is that light exists as individual photons but travels in the form of waves, like molecules of water.

The problem with light is that it travels, it would appear, without itself being a phenominum propogated in a carrier medium, i.e., air or water.

We are used to thinking of things as traveling in some sort of medium, sound in air when sound actually is a mechanical vibration of air, water waves when the waves are actually a mechanical vibration of water, electricity not as a wave but as an atomic particle which is actually a transfer in wire of electrons from atom to atom of the metal the wire is composed of.

So what is the medium through which light travels insofar as we know that it travels through the vacuum of space? Photons, they say, have no mass. That seems itself to be an expression of the appearing fact that they are not a vibration of water, air, or space which is vacuum.

I am aware that what I have done here is attempt to more precisely in language define the physical things we are speaking here, i.e., sound, light, etc.

I must admit I am thinking out loud because I have long been curious about all the curious expression as to the Young slit experiment, some in fact quite mystical when all that exists is matter/energy.

But, comment on what I have said about your first sentence above. I think that you were trying to say what I have said at length, that physical manifestations of air/sound, and the mechanics, truly mechanical, of hearing them are different from the vibrations of light, electromagnetic waves, which are a different phenomena, although appearing in a similar vibrating format, suggesting a unity at some level.

As I suspect we all know there are beat frequencies produced by electromagnetic waves but they are not necessarily the function we see when we perceive light/color.

All this makes me think of the so-called "quantum mysteries," actually and simply unknowns the solution for which we do not have sufficient data, and the invisible and "missing" black mass of the universe.

Who knows? Maybe we will solve the quantum mysteries right here on this web site.

j.

Hi Jack,

This was in response to a comment by cnpower on a side issue of beat frequencies in linear and non linear media. The point that I was making is that in the ear we have thousands of receptors, each attuned to only a very small bandwidth of the audio spectrum, giving us a very accurate system to discern pitch. This is in contrast to the eye which has only three types of receptors each covering a very wide bandwidth to deal with the visual spectrum. The ear can actually 'nail' an individual frequency, just like a spectrometer can 'nail' a specific wavelength of light, while the eye with its limited range of receptors has to determine color (wavelength) by 'interpolation'.

...I think that air itself is a nonlinear medium, so the beat frequency is not a function of the hearing method

Its not difficult to prove this subject. use two signals in the field (not in a room, as the room can produce stand wave easily). then use a mic to recieve these two signals and then send to a oscillascope, to view the wave shape. if the air has a nonlinear transform feature, you will see a beat frequency on the screen. otherwise, you will see two signals individually.

This is also one way that we often used to test an amplifier behavior good or not. as well as speaker, mic etc.

now you will clear that at where the nolinear take place?

----if the air has a nonlinear transform feature, you will see a beat frequency on the screen. otherwise, you will ...

none like to point out there is something wrong with the above words?

its pity.

Im waiting until specialists point out the wrong among the words.

Hi cn,

I'm uneasy about this. I can't see how a microphone will work any differently than an ear. I like the experiment you suggest, and I'm lining up the equipment to try it. I want to use one electric guitar slightly detuned into an amp, two detuned electric guitars into one guitar amp with a microphone, two guitars each with its own amp into a microphone, and two guitars directly into the oscilloscope, bypassing the microphone. I'll let you know what I find, but to me it seems to me that since air has some mass it will be a non-linear medium. Maybe I'm wrong. I definitely agree that this should be done outdoors. I hope the neighbors don't mind.

Hi,John,

Why not use a signal generator instead of the two guitars?

that will make you easy to test. and view on screen of oscilloscope.

if you use guitar as sample, you'd better use storage oscilloscope to compare waveform.

somebody still said the air is nonlinear medium as well. I remmeber.

when sound energy transport throught it, you have to take account of temperature and convey to heat from sound etc. becaseu air molecule movement.

Im waiting for your news

there's an interesting history of color tv on wikipedia though it doesn't have the technical detail you're seeking;

http://en.wikipedia.org/wiki/Color_television