Physical parameters define colors like the pigment primaries

3,036
3
What physical parameters define colors like the pigment primaries - red, blue and yellow - and their mixtures? How about light primaries?
 

cepheid

Staff Emeritus
Science Advisor
Gold Member
5,176
35
What do you mean by physical parameters? The wavelength of light determines its colour, but I guess you already knew that. As for pigments, if you mean, what property of a substance determines its colour, then I guess that has to do with atomic structure or is quantum mechanical. Primary pigments absorb one of the primary colours (wavelengths) and reflect the others.
 
3,036
3
My question is basically: what frequencies are assigned to which primary colors, and what is the mechanism that would describe secondary colors as primary combinations corresponding to single frequencies?
 
418
3
Just look up the EM wavelength chart. Different colors are at different wavelengths.
 
3,036
3
That chart is more qualitative than physical regarding a precise definition for primary and secondary colors. Please refer to my previous post. E. g., what is the exact frequency or range of frequencies for the color blue, and how is green defined as a mixture of yellow and blue frequencies?
 
418
3
You perceive Yellow & Blue as green but it's not really green. Its all about how your eye and brain perceives colors, your eye can't distinguish between real green light and the mixture of yellow and blue. A very interesting question you can ask is if you have a yellow and blue dot seperated by a distance x , how far away do you have to be to see green? For the color/wavelengths I will again refer you to a EM chart, it's out there.
 
my question is, can anyone?
when you see blue and green light,
don't the wavelenghts add up to green anyways?
wave-wise
 
418
3
No, it's biology of the eye. It's all about the cones and rods, but mostly cones for color.
 
so wavelenght-wise two waves, a blue and a yellow, arent the same as one, a green?
they look the same but they are not?
im confused
 
418
3
I'll refer you too any of the good references on color vision. You're getting into more biology.
 
3,036
3
Maybe, in part, colors are defined by the blackbody spectrum of the sun.
 
418
3
No, color is not defined by blackbody radiation.
 

Gokul43201

Staff Emeritus
Science Advisor
Gold Member
6,907
13
The answer lies primarily in the phototransduction mechanism in the eye, but there's a rough connection with averaging wavelengths as well. I'm certainly not qualified to discourse on this with any authority, but from my scant understanding...

...the crude version of the mechanism involves photoexcitation in the retina. Each such event creates a mobile electron-ion pair of related energy, which affect the membrane potential of the photoreceptor. This potential is what gets coded as a color.
 
Last edited:

The Physics Forums Way

We Value Quality
• Topics based on mainstream science
• Proper English grammar and spelling
We Value Civility
• Positive and compassionate attitudes
• Patience while debating
We Value Productivity
• Disciplined to remain on-topic
• Recognition of own weaknesses
• Solo and co-op problem solving
Top