How can RGB reproduce all (most) colours?

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In summary, the conversation discusses the concept of using red, green, and blue frequencies to produce different colors, and how this relates to the function of receptors in the human eye. The conversation also touches on the limitations of this color system and provides a resource for further reading.
  • #1
jodyflorian
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Hiya,

While learning about photography I've realized that there's something I can't explain with the physics I was taught at school.

What I do know is that pure red, green and blue have specific frequencies. And that combining the colours produces white. And although I don't know exactly why, I've read that red, green and blue together can approximate most colours - it has a limited "gamut" although personally I can't spot the deficiency.

My main questions are...
1) How can those frequencies produce colours at frequencies different to themselves? e.g. yellow
2) And I thought white was the visual equivalent of white noise (broad band) so how can that be produced with RGB?

Has it got anything to do with how the receptors in our eyes work? Back to biology now lol I remember there existing RGB sensitive cells... it's sounding less and less like a coincidence! Does that mean a green receptor would react to frequencies on either side? Just guessing now...
 
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  • #2
Your 3 is right, it has everything to do with receptors. IOW it is a question of physiology not physics.

Just rough principle since I think the explanation is here on this site somewhere in more detail and very many textbooks, you have 3 types of receptors with response spectra spread but centred on R G or B. Some pure wavelength you ask about will produce a given response on all 3, proportions different according to that wavelength. So each pure wavelength corresponds to a unique combination for you neural biocomputer amd it distinguishes thousands of them.
 
  • #3
Sorry for the physiology post :p

Thanks - now I know what to look into next :)
 
  • #4
Wiki has a reasonable article. The 3 sets of receptors on most human eyes, each with maximum sensitivity at some frequency, but the sensitivity peaks are not "exactly" red, blue, and green.

http://en.wikipedia.org/wiki/Color
 
  • #5
jodyflorian said:
it has a limited "gamut" although personally I can't spot the deficiency.

Compare the "orange" patch in wikipedia's article (The colors of the visible light spectrum), which is (R=255, V=128, B=0) and has a 100% saturation, to the color of an orange skin or a clementine skin !
 

1. How does RGB reproduce all colors?

The RGB color model is based on the concept of additive color mixing. This means that by combining different amounts of red, green, and blue light, all visible colors can be created. The varying intensities of these three primary colors result in millions of different color combinations, allowing RGB to reproduce all colors.

2. Can RGB reproduce all colors accurately?

In theory, yes. However, the ability to accurately reproduce colors also depends on the device displaying the RGB colors. Monitors and screens can vary in their color display capabilities, so there may be slight discrepancies in the color reproduction. Additionally, the human eye can perceive colors differently, so what may appear as one color to one person may look slightly different to another.

3. Are there any limitations to RGB's color reproduction?

While RGB can produce a vast range of colors, it does have some limitations. It is not able to reproduce colors outside the visible spectrum, such as infrared or ultraviolet. Additionally, RGB cannot accurately reproduce colors that are outside of its gamut, or color range. This is why some colors may appear dull or different when viewed on a screen compared to their real-life counterpart.

4. How does the RGB color model compare to other color models?

RGB is just one of many color models, each with its own way of producing colors. Other commonly used color models include CMYK, which is used for printing, and HSB, which is based on hue, saturation, and brightness. While each color model has its strengths and weaknesses, RGB is widely used because of its ability to accurately reproduce colors on electronic displays.

5. Can RGB produce all colors found in nature?

RGB is limited to producing colors that are within the visible spectrum, which is the range of colors that the human eye can see. This means that it can produce most colors found in nature, but there are some colors, such as ultraviolet and infrared, that cannot be accurately reproduced using RGB. Additionally, RGB cannot reproduce colors with certain properties, such as metallic or fluorescent colors.

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