The true look of lights

[Hasan Özel]

Hi Everyone,

I want to know that which one these case is correct, Case 1 or Case 2. I mean, Is the visible spectrum as bright as on the right side or as dull as on left side in reality ? For example,the appearance of monochromatic yellow (570-590 nm) and cyan (475-495 nm) light looks like as Case 1 or Case 2. In other words, Is there any difference between monochromatic yellow-cyan lights and [yellow=green+red(500-730 nm)]-[cyan=blue+green(380-570 nm)] lights shown like on figure ?

[MaximThibodeau]

Maybe you are doing reference with Biology, the brain receive electro-chemical info about the eyes receptor. You mean, does, the Humain brain-eyes system, averaging correctly the wave spectrum ?  Will your answer be case 1, if you could decrease the luminosity of my screen only for that squares, and not playing on color itself ? Please put some calculation... 

[studiot]

Don't the colours on the left have added grey?

[koti]

Depends on the technology representing colors. Yellow will look a lot different printed on cloth, paper or sprayed onto a metal surface or displayed on a TV screen. Generally colors represented by the RGB model look more vibrant due to a source of light which is needed for the RGB color model. CMyK colors are usually more dull and not as saturated because they are seen only by reflected light.

The colors in the picture on the left look like printed CMYK and the colors on the right look like CMYK displayed on a monitor.

[MaximThibodeau]

Im giving a try:

Yellow: 590 - 570 = 20

The yellow color in eyes referential:

green + red: 730 - 500 = 230

minus the yellow = 210

The energy difference (within some pigment behavior): More energy in the eyes referential, but the same color.

The color in case 1, modified by the eyes referential, darker, please...

 

[Sensei]

1 hour ago, studiot said:

Don't the colours on the left have added grey?

Perfect yellow in RGB color model is 255,255,0 and in HSV/HSB it's 60,255,255 (Hue is in 0...360 range, Saturation/Value/Brightness in 0..255, but could be in 0...100%)

Darker yellow on the left has HSV/HSB with ~50% Value/Brightness (RGB 127,127,0 in HSV/HSB 60,255,127).

 

Couple times I was making color model converters from RGB <-> HSB/HSV in C/C++ ...

 

 

Edited April 2, 2018 by Sensei

[swansont]

11 hours ago, MaximThibodeau said:

Im giving a try:

Yellow: 590 - 570 = 20

The yellow color in eyes referential:

green + red: 730 - 500 = 230

minus the yellow = 210

The energy difference (within some pigment behavior): More energy in the eyes referential, but the same color.

The color in case 1, modified by the eyes referential, darker, please...

 

This was meaningless the first time you posted it, and is still meaningless.

13 hours ago, Hasan Özel said:

Hi Everyone,

I want to know that which one these case is correct, Case 1 or Case 2. I mean, Is the visible spectrum as bright as on the right side or as dull as on left side in reality ? For example,the appearance of monochromatic yellow (570-590 nm) and cyan (475-495 nm) light looks like as Case 1 or Case 2. In other words, Is there any difference between monochromatic yellow-cyan lights and [yellow=green+red(500-730 nm)]-[cyan=blue+green(380-570 nm)] lights shown like on figure ?

One problem is that you aren't showing lights, you're showing a computer-rendered picture, and computers use light addition to form their colors. There is no way for you to represent "monochromatic" yellow or cyan on an RGB monitor.

[Hasan Özel]

35 minutes ago, swansont said:

This was meaningless the first time you posted it, and is still meaningless.

One problem is that you aren't showing lights, you're showing a computer-rendered picture, and computers use light addition to form their colors. There is no way for you to represent "monochromatic" yellow or cyan on an RGB monitor.

The figure is symbolic to help explain the question. I want to say that the apperance of monochromatic lights yellow(570-590 nm) and cyan(475-495 nm) are the same or not,comparing to yellow(500-730 nm)=red+green and cyan(380-570 nm). I mean if we make two sample which the first one is only reflects monochromatic light(i.e yellow(570-590 nm) and the other reflect wider range(i.e yellow(500-730 nm)=red+green),are they have the same apperance ?

Another point is that visible spectrum light components are dull as case 1 or bright as case two ?

Because at electronical light device, yellow+blue or green+magenta or cyan+red combination makes white light but monochromatic combination can not.(i.e monochromatic yellow+monochromatic blue does not equals to white light)

12 hours ago, MaximThibodeau said:

Im giving a try:

Yellow: 590 - 570 = 20

The yellow color in eyes referential:

green + red: 730 - 500 = 230

minus the yellow = 210

The energy difference (within some pigment behavior): More energy in the eyes referential, but the same color.

The color in case 1, modified by the eyes referential, darker, please...

 

I mean, in fact yellow objects which looks like in case 2, not only reflects monochromatic yellow light also reflects a wider range between green-red part of spectrum (500-730 nm). If only reflects monochromatic yellow light,it looks like as case 1. This argument is true or false ?

53 minutes ago, swansont said:

This was meaningless the first time you posted it, and is still meaningless.

One problem is that you aren't showing lights, you're showing a computer-rendered picture, and computers use light addition to form their colors. There is no way for you to represent "monochromatic" yellow or cyan on an RGB monitor.

I know but this is just figure to help explain idea. We can take as electromagnetic spectrum case 1 and case 2. Is the electromagnetic spectrum as dull as case 1 or as bright as case 2 ?

[Strange]

So, you are asking if the eye can perceive any difference between a particular shade of yellow produced by a monochromatic source and the same yellow produced by two (or more) frequencies?

The trouble is, as far as I can see, is that the only way of defining the "same" yellow by combining multiple frequencies is by how it looks. In which case, by definition, they will look the same. Colour is a function of perception not something that can be defined independently of how we see it.

In general, you can produce the same effect from a single frequency (that partially stimulates two sets of photoreceptors whose frequency responses overlap) as you can with two different frequencies that each stimulate one set of photoreceptors. By adjusting the frequencies and intensities, you can make it match "exactly" (as reported by the person viewing it) the same.

(You might want to look up "qualia" in an introductory philosophy text.)

[Hasan Özel]

If there is a no difference between monochromatic yellow(570-590 nm) and yellow(500-730 nm)=red+green lights,is this also acceptable for objects which the first one is only reflecting monochromatic yellow light(570-590 nm) and the second one is reflecting wider range(500-730 nm) yellow=red+green ?

1 hour ago, Strange said:

So, you are asking if the eye can perceive any difference between a particular shade of yellow produced by a monochromatic source and the same yellow produced by two (or more) frequencies?

The trouble is, as far as I can see, is that the only way of defining the "same" yellow by combining multiple frequencies is by how it looks. In which case, by definition, they will look the same. Colour is a function of perception not something that can be defined independently of how we see it.

In general, you can produce the same effect from a single frequency (that partially stimulates two sets of photoreceptors whose frequency responses overlap) as you can with two different frequencies that each stimulate one set of photoreceptors. By adjusting the frequencies and intensities, you can make it match "exactly" (as reported by the person viewing it) the same.

(You might want to look up "qualia" in an introductory philosophy text.)

If there is a no difference between monochromatic yellow(570-590 nm) and yellow(500-730 nm)=red+green lights,is this also acceptable for objects which the first one is only reflecting monochromatic yellow light(570-590 nm) and the second one is reflecting wider range(500-730 nm) yellow=red+green ?

[Strange]

29 minutes ago, Hasan Özel said:

If there is a no difference between monochromatic yellow(570-590 nm) and yellow(500-730 nm)=red+green lights,is this also acceptable for objects which the first one is only reflecting monochromatic yellow light(570-590 nm) and the second one is reflecting wider range(500-730 nm) yellow=red+green ?

I don't think there is an easy answer (except by looking at them). The mathematics and psychology of colour perception are quite complex.

https://en.wikipedia.org/wiki/Color_vision#Mathematics_of_color_perception

[studiot]

43 minutes ago, Hasan Özel said:

If there is a no difference between monochromatic yellow(570-590 nm) and yellow(500-730 nm)=red+green lights,is this also acceptable for objects which the first one is only reflecting monochromatic yellow light(570-590 nm) and the second one is reflecting wider range(500-730 nm) yellow=red+green ?

 

Did you miss my question or did you not understand it?

There clearly is a difference between narrow band light and wideband light, which includes some of the original narrow band.

Further the statement "this is also aceptable.... etc" makes no sense.

So please restate you question and premise.

 

 

 

[Hasan Özel]

29 minutes ago, studiot said:

 

Did you miss my question or did you not understand it?

There clearly is a difference between narrow band light and wideband light, which includes some of the original narrow band.

Further the statement "this is also aceptable.... etc" makes no sense.

So please restate you question and premise.

 

 

 

I miss,this was my fault,I am sorry for this. ☺️

Can we say like this,the yellow(500-730 nm)=red+green light is brighter than monochromatic yellow light (570-590 nm) ?

[Strange]

14 minutes ago, Hasan Özel said:

Can we say like this,the yellow(500-730 nm)=red+green light is brighter than monochromatic yellow light (570-590 nm) ?

It depends how bright each one is.

The brightness depends mainly on the amplitude (and also on the wavelength, but less so).

[Hasan Özel]

2 hours ago, Strange said:

It depends how bright each one is.

The brightness depends mainly on the amplitude (and also on the wavelength, but less so).

So we can say that, If both of lights( monochromatic yellow(570-590 nm) and yellow=red+green(500-730 nm)) have the same intensity, yellow=red+green(500-730 nm) is more lighter(brighter) than monochromatic yellow(570-590 nm).

Thank you 

I understood from your link that there is a difference between monochromatic yellow(570-590 nm) and yellow=red+green(500-730 nm). These two lights or colors which reflect these lights have different appearence from each other. 

Edited April 3, 2018 by Hasan Özel

[Strange]

Just now, Hasan Özel said:

So we can say that, If both of lights( monochromatic yellow(570-590 nm) and yellow=red+green(500-730 nm)) have the same intensity, yellow=red+green(500-730 nm) is more lighter(brighter) than monochromatic yellow(570-590 nm).

If they have the same intensity, then I would assume they will appear equally bright.

[studiot]

4 hours ago, Strange said:

If they have the same intensity, then I would assume they will appear equally bright.

 

No because the appearance of brightness depends upon the response curve of the eye.

 

6 hours ago, Hasan Özel said:

I miss,this was my fault,I am sorry for this. ☺️

Can we say like this,the yellow(500-730 nm)=red+green light is brighter than monochromatic yellow light (570-590 nm) ?

 

The point I am trying to make  is that pure colour (monochromatic light) has a very narrow band, perhaps even narrowere than your 570-590 nm.

Grey is a mixture of certain proportions of all the primary coulours (I forget the proportions but they could be looked up).

Grey is also regarded as the universal neutral colour.

 

Edited April 3, 2018 by studiot

[Strange]

16 minutes ago, studiot said:

No because the appearance of brightness depends upon the response curve of the eye.

Good point. 

[StringJunky]

1 hour ago, studiot said:

 

No because the appearance of brightness depends upon the response curve of the eye.

 

 

The point I am trying to make  is that pure colour (monochromatic light) has a very narrow band, perhaps even narrowere than your 570-590 nm.

Grey is a mixture of certain proportions of all the primary coulours (I forget the proportions but they could be looked up).

Grey is also regarded as the universal neutral colour.

 

Grey is a tone, not a colour. It represents reflectance not hue. In hue terms, white through to black are neutral.

[Hasan Özel]

1 hour ago, Strange said:

Good point. 

I think this is the key, your reference link explains very well https://en.wikipedia.org/wiki/Color_vision#Mathematics_of_color_perception

The yellow(500-730 nm)=red+green has a difference comparison to monochromatic yellow(570-590 nm) perhaps even narrower than 570-590 nm as Studiot said, if we go back to beginning of topic, monochromatic visible spectrum lights are dull like case 1, not bright as case 2. I understood this 

10 minutes ago, StringJunky said:

Grey is a tone, not a colour. It represents reflectance not hue. In hue terms, white through to black are neutral.

I want to know that which one these case is correct, Case 1 or Case 2. I mean, Is the visible spectrum as bright as on the right side or as dull as on left side in reality ? For example,the appearance of monochromatic yellow (570-590 nm) and cyan (475-495 nm) light looks like as Case 1 or Case 2. In other words, Is there any difference between monochromatic yellow-cyan lights and [yellow=green+red(500-730 nm)]-[cyan=blue+green(380-570 nm)] lights shown like on figure ?

What are you think about this sir ? I also want to learn your ideas 

Edited April 3, 2018 by Hasan Özel

[StringJunky]

11 minutes ago, Hasan Özel said:

I think this is the key, your reference link explains very well https://en.wikipedia.org/wiki/Color_vision#Mathematics_of_color_perception

The yellow(500-730 nm)=red+green has a difference comparison to monochromatic yellow(570-590 nm) perhaps even narrower than 570-590 nm as Studiot said, if we go back to beginning of topic, monochromatic visible spectrum lights are dull like case 1, not bright as case 2. I understood this 

 

Quote

 

I want to know that which one these case is correct, Case 1 or Case 2. I mean, Is the visible spectrum as bright as on the right side or as dull as on left side in reality ? For example,the appearance of monochromatic yellow (570-590 nm) and cyan (475-495 nm) light looks like as Case 1 or Case 2. In other words, Is there any difference between monochromatic yellow-cyan lights and [yellow=green+red(500-730 nm)]-[cyan=blue+green(380-570 nm)] lights shown like on figure ?

What are you think about this sir ? I also want to learn your ideas 

Quote

The Principle of Univariance

Most individuals are “trichromatsâ€, having three cone types, with peak sensitivity to long-, middle-, and short-wavelengths (L, M, S). An individual cone response varies in the degree to which it is activated, which depends on two variables:

the wavelength of absorbed light; andthe intensity of the light (the amount of light).

Wavelengths that match the spectral sensitivity of the cone type will be absorbed more readily and cause more activation of the cone; more intense light will also be absorbed more readily and cause more activation. The same cone could therefore respond in the same fashion to different wavelengths (say, long and middle) as long as the intensity is adjusted appropriately. This is known as the principle of univariance. As a result, a single cone response by itself cannot tell the brain the color of the stimulus. Color vision is achieved only in the presence of two or more cones with overlapping but different spectral sensitivity curves.

Any physical stimulus that elicits the same activity from the cones will appear the same. Because of the broad absorption curves of the cones, there are many physical stimuli (with different spectral distributions) that will elicit the same cone activity. These are referred to as metamers. The best example of metamers is yellow: consider monochromatic yellow—the region of the spectrum that appears yellow. This is physically entirely different than a mixed yellow made by mixing red and green light, yet the two yellows could be indistinguishable to normal trichromats.  http://academics.wellesley.edu/Neuroscience/Neuro320/Coursecontent/colorintheeye.html

 

[Hasan Özel]

31 minutes ago, StringJunky said:

1) The wavelength of absorbed light

2) The intensity of the light (the amount of light).

 

I think there is difference what I said.

In this article, yellow=red+green is aritmetic mean of green(500-570 nm) and (620-730). If we make this calculation yellow looks like(560-650) which is so close monochromatic yellow light(570-590 nm). If we describe a yellow=red+green between 500-730 nm,this light is different than the first two situations. I think this is the key, when we create a yellow light which is red+green, we also use two monochromatic light green(500-570 nm) and red(620-730 nm), so this is yellow=red+green make the same effect like monochromatic yellow light and this light is also has a narrow range which yellow(500-730 nm) described by me. I hope I can explain myself 

Edited April 3, 2018 by Hasan Özel

[StringJunky]

28 minutes ago, Hasan Özel said:

I think there is difference what I said.

In this article, yellow=red+green is aritmetic mean of green(500-570 nm) and (620-730). If we make this calculation yellow looks like(560-650) which is so close monochromatic yellow light(570-590 nm). If we describe a yellow=red+green between 500-730 nm,this light is different than the first two situations. I think this is the key, when we create a yellow light which is red+green, we also use two monochromatic light green(500-570 nm) and red(620-730 nm), so this is yellow=red+green make the same effect like monochromatic yellow light and this light is also has a narrow range which yellow(500-730 nm) described by me. I hope I can explain myself 

It appears that this subject is called 'metamerism'.

Quote

In colorimetry, metamerism is a perceived matching of the colors with different (nonmatching) spectral power distributions. Colors that match this way are called metamers.

A spectral power distribution describes the proportion of total light given off (emitted, transmitted, or reflected) by a color sample at each visible wavelength; it defines the complete information about the light coming from the sample. However, the human eye contains only three color receptors (three types of cone cells), which means that all colors are reduced to three sensory quantities, called the tristimulus values. Metamerism occurs because each type of cone responds to the cumulative energy from a broad range of wavelengths, so that different combinations of light across all wavelengths can produce an equivalent receptor response and the same tristimulus values or color sensation. In color science, the set of sensory spectral sensitivity curves is numerically represented by color matching functions.  https://en.wikipedia.org/wiki/Metamerism_(color)

 

[studiot]

10 hours ago, StringJunky said:

Grey is a tone, not a colour. It represents reflectance not hue. In hue terms, white through to black are neutral.

Indeed they are and it is 20 years+ since I threw out my (then) old university notes on Environmental Engineering including illumination.

I have been trying to think of a simple one paragraph explanation of the role of grey.

 

Hasan, it is good to have someone interested in the subject, especially as the last persion wanting to 'discuss' colour perception was a troll.

So here goes.

 

Illimination and the visual perception of illuminated object a very complicated subject because of the interaction between the the source, the light itself and the illuminated objects.

This is not helped by the fact that the relationships change with the intensity (and sometimes other parameters such as direction) of the illuminating light.

So first off there are standards to refer to.
One of these is the CIE 'Standard Sky'

https://www.google.co.uk/search?q=CIE+standard+sky&ie=utf-8&oe=utf-8&client=firefox-b&gfe_rd=cr&dcr=0&ei=aIbEWpesJo-Btgfb56fIBQ

When we (or a recording machine such as a camera) view an illuminated object we see two separate aspects of the incident light.

We see the

level or intensity as a measurement we call the Luminance and

The perceived colour or Chrominance.

 

These are not independent and at very low levels of light we can only see the Luminance. That is we cannot see colour.

 

The Luminance property by itself allows us to create a monchrome or greyscale model of the image, point by point.
This is how early fax machines, photocopiers, the silver screen at the cinema and old fashioned 'black and white' television work.

The luminance is a simple single numerical value that specifies the light density.

 

The chrominance is much more complicated and is not a single value but has to be represented by a collection of several numbers that indentify it on a two or three dimensional chart.

This is further complicated by the fact that there are several different charts schemes available and each includes a different overall range of the light spectrum, known as the (colour) gamut. So some colours appear in one scheme but not in others.

But having chosen the scheme it does not end there because we see with two eyes and each of our eyes sees a slightly different colour emanating from each point on the object in view.
This is because the light is affected by shading and other effects from nearby points and perhaps also from the light source itself.

Amazingly our brain is able to filter out these differences and assemble a coherent unique colour value for any point on the illuminated object.

 

Here is a good semi technical introduction to the subject.

https://www.konicaminolta.eu/fileadmin/content/eu/Measuring_Instruments/4_Learning_Centre/C_A/PRECISE_COLOR_COMMUNICATION/pcc_english_13.pdf

 

 

[Mehmet Saygın]

On 02.04.2018 at 11:54 PM, Hasan Özel said:

Hi Everyone,

I want to know that which one these case is correct, Case 1 or Case 2. I mean, Is the visible spectrum as bright as on the right side or as dull as on left side in reality ? For example,the appearance of monochromatic yellow (570-590 nm) and cyan (475-495 nm) light looks like as Case 1 or Case 2. In other words, Is there any difference between monochromatic yellow-cyan lights and [yellow=green+red(500-730 nm)]-[cyan=blue+green(380-570 nm)] lights shown like on figure ?

I think this is the answer of your question.

There is a difference between monochromatic yellow (570-590 nm) and yellow(500-730 nm),but not as you think.

Yellow = Green(500-570 nm) +Red (620-730 nm) light and monochromatic yellow(570-590 nm) is the same thing,because our eyes integrates Green+Red=Yellow and this combination of the light also a narrow range likes monochromatic yellow. But yellow(500-730 nm) is a different light,this light has a wider range and continuous spectrum. Both monochromatic yellow light and Yellow = Green(500-570 nm) +Red (620-730 nm) light has a lemonish yellow color. On the other hand, yellow(500-730 nm) has a creamy white color. This is the key. 

Edited April 4, 2018 by Mehmet Saygın