A Extracting Color from a Spectral Date

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The discussion centers on extracting color from a spectral dataset characterized by wavelength, refraction index, and absorption coefficient. Participants clarify that while wavelengths are measurable physical properties, color is a physiological perception influenced by various factors, including the illuminant and the surface finish. The absorption spectrum indicates that the peak wavelength corresponds to the most absorbed light, suggesting that the visible color will be in the longer wavelengths, primarily red. However, determining a "dominant wavelength" is deemed insufficient for accurate color representation, as the entire spectrum contributes to perceived color. For rendering simulations, understanding the impact of the illuminant and the specific characteristics of the material is crucial for achieving a true color match.
VitorsSantiago
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Hello everybody,

I would love some help on the following; I have a spectral date (As image 1 below) formed by the wavelength, refraction index and the absorption coefficient. Is there any way to relate this spectral date to a dominant wavelength? or in a few words extract the color from this spectrum?

1645125148076.png


1645125484839.png


This information is also found in the spectrum file, I believe it is also usable in some way to calculate the dominant wavelength:

1645125235146.png


The real dominant color of this object is part of the red spectrum.
 
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If you look through the substance you should see mainly wavelengths above about 600 nm, so it should look red. The color is not a single wavelength, but a whole range, in this case longer than about 600 nm.
 
Color is not a physical but a physiological entity. In this sense it's much more complicated than the physical description of light as an electromagnetic field.
 
vanhees71 said:
Color is not a physical but a physiological entity. In this sense it's much more complicated than the physical description of light as an electromagnetic field.
So you're telling me color is not a physical property? These data were obtained by reading the spectrometer, that is, it is a measurable characteristic. Sorry if I sounded ignorant, it's not really my area of expertise
 
vanhees71 said:
What you measure are wavelengths, i.e., physical properties of electromagnetic waves but not color, which is a physiological quantity:

https://en.wikipedia.org/wiki/Color
Oh ok, I get it, it really makes perfect sense. But do you know if there is any way to determine the dominant wavelength from this spectrum I showed above?
 
VitorsSantiago said:
But do you know if there is any way to determine the dominant wavelength from this spectrum
You can see yourself on the plot where the curve peaks. But may I suggest that "dominant wavelength" may not be a useful concept in cases like this. The entire spectrum contributes to the effects, not just one frequency.
 
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anorlunda said:
You can see yourself on the plot where the curve peaks. But may I suggest that "dominant wavelength" may not be a useful concept in cases like this. The entire spectrum contributes to the effects, not just one frequency.

Got it, so the peak wavelength represents the dominant, this is a very useful information.
Just to clarify, what I'm trying to do is a rendering simulation, and I would like to apply the "true" color (Or at least as close as possible.) of that specific material, in which one of the inputs to insert the color in the software is the wavelength. However, using this peak value found in the spectrum above, the software calculates the color displaying an orange tone, different from the real one. I will try to think more about the matter in trying to relate the values obtained.

Anyway, if anyone has any more information I would be grateful.
 
VitorsSantiago said:
Got it, so the peak wavelength represents the dominant, this is a very useful information.
Just to clarify, what I'm trying to do is a rendering simulation, and I would like to apply the "true" color (Or at least as close as possible.) of that specific material, in which one of the inputs to insert the color in the software is the wavelength. However, using this peak value found in the spectrum above, the software calculates the color displaying an orange tone, different from the real one. I will try to think more about the matter in trying to relate the values obtained.

Anyway, if anyone has any more information I would be grateful.
The curve you show is an absorption spectrum. This means that the peak is the wavelength that is absorbed most! If you look through this substance at a source of white light you will see the light that's not absorbed, which is mainly 570 nm and longer, so the substance should look red.
 
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Philip Koeck said:
The curve you show is an absorption spectrum. This means that the peak is the wavelength that is absorbed most! If you look through this substance at a source of white light you will see the light that's not absorbed, which is mainly 570 nm and longer, so the substance should look red.
This is absolutely correct. Also you have not mentioned the illuminant which will further influence the perceived color. The graph mentions illuminant A which is a ~3000K tungsten lamp. This will also affect the perceived color.
So to quantify the perceived color you need to know the surface "finish", the exact illuminant, the absorbtivity of the surface as a function of wavelength and angle, and the illumination geometry. In addition you need to have the spectral response curves for the three chromophores in your eyeball.
Even then it is tricky. For instance you may need to be aware of metameric colors:
https://en.wikipedia.org/wiki/Metamerism_(color)
Frankly "dominant wavelength" in this context is not well defined.
It is in fact more complicated and requires greater specificity.
 
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VitorsSantiago said:
Anyway, if anyone has any more information I would be grateful.
I still don't think that you are getting the idea that everyone is trying to convey. No single frequency or wavelength will get you where you need to go.

Try spending some time with this color wheel
https://www.rapidtables.com/web/color/color-wheel.html

You'll see not only color, but also brightness and saturation, and for each color, you see the blends of R, G and B needed to create it. Perhaps you can find the color you desire on the wheel, and then read out the mix of colors you need to do it.
 
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