How many colors are there?

I know that there is a certain number of primary colors but how many colors are there all together? Are there really any new colors?

There are only two colours, but they fade into each other.

Arent all colours just made up of different combinations of the three types of cones in the retina - red, blue and orange. I will look for the lambda max’s for each.

Well, there’s ROY G BIV, infrared, ultraviolet, and all the blends in between.

Are you asking how many colors can humans detect as different?

I would think that theoretically, there are an infinite number of colors.

There are either 3, 17 million, infinite, or none, depending on what time it is.

My video card says it can distinguish 16.7 million colors. However, while my computer may be able to distinguish that many colors but I doubt I could.

I’d wager there are more than 16.7 million colors though as one could presumably keep making finer and finer adjustments. There is bound to be a limit to this (light has to be emitted in discrete packets…you can’t just subdivide forever) but the final total is probably quite large.

Just a WAG though.

I’m not sure how one could say that there are any finite number of colors. Consider: If you mix yellow and blue paints in equal proportion, you’ll get green. If you mix one part yellow to two parts blue, you’ll get a bluish green. If you mix one part yellow with ten parts blue, you’ll get something that’s very close to blue, but still a little greenish. Likewise, you could mix one part yellow with a million parts blue, or a billion. There are an infinite number of possible ratios you could use, and each one would give you a slightly different color. And that’s just shades of green.

DrFidelius they sell colour TVs now.

Yes, there are an infinite number of colors, as you can keep halving wavelengths ad infinitum. It’s been many years now that computer graphics cards have offered up 16.7 million colors.

But your eye likely cannot distinguish anywhere near that many. For graphics displays that convey information by color banding, we try to keep it to 32 or less, preferably 16.

A photograph with 32 or less will appear banded, but most eyes will not be notably assaulted by color banding with a 256 level color scale.

Not infinite. Planck’s constant defines discrete differences in energy that photons can have, and therefore wavelengths. In any case, IIRC, the human eye is capable of distinguishing about 2 million colors.

But human eyes can’t distinguish an infinite number of colors.

Most computer monitors can display 256 shades of each primary color, which means 256^3=16 million possible combinations. That’s close enough to “infinite” for most purposes. Some older computers had 32 shades each, or about 32,000 possible combinations. On those displays, when you try to display a smooth gradient (like a photo of a twilight sky) you could see distinct bands of separate colors. Even older computers had 256 colors total, and those look pretty bad.

Right, not truly infinite. But effectively for our eyes.

Not correct. Quantum mechanics as a whole (not just Planck’s constant) does say that a bound electron (such as one in an atom) can only emit light at certain discreet wavelengths, but light emitted by a free electron can have any frequency at all. Even with bound electrons, the wavelengths are smeared out a bit by the uncertainty principle and Doppler shifts, and even if only discreet wavelengths were available, you could still produce an infinitude of colors by mixing monochromatic light sources in various proportions.

Wow - answer the phone and there are a dozen replies.

shows the absorption spectra of the three types of cones. They peak at purplish-blue (445nm), yellowish green (535nm) and orange (575nm). All colours are made up of these. So there are an infinite range of combinations and shades, different brains can discern more hues than others - all depend on the person.

As I remember from my computer graphics course, the eye has three types of receptors for colour which respond diferently according to the different spectral distribution of (colored) light.
Although these receptors are commonly called “red” “green” and “blue”, they actually respond in a more complex manner. Actually, combining red, green and blue light, you can create only a subset of all the colours that the eye can see.
There is a french standards organization called the CIE that created a so called “chromaticity diagram” based on three fundamental components (other than red green and blue). This diagram represents all the colours that the eye can possibly perceive. Note that a rendering of the diagram on your computer monitor can never be exact, because the monitor uses red green and blue phosphor.
Just look for “CIE diagram” on Google.
As for how many colors can the eye distiguish, I guess it all depends on how many subtle differences in shade and tone one can distinguish on the the color space of the CIE diagram. I can’t remember, but I think the average is something like 150 different hues. This means 150 different saturated colurs (bright pure colours with no white). This doesn’t include different levels brightness nor different degrees of saturation.
This is a big subject, so I may have oversimplified some things.


Really? Wow! I gotta try that.

I don’t want to start a new thread on this as it fits in here rather well…

Is there any consensus as to what is “white?”

I know our brains automatically adjust to different light sources, and 18% grey has long been a standard in cinema and photography.

But, just what is white?

Is color wavelength or frequency? I thought it was wavelength but I admit I am now confused (there’s a news flash) and don’t really know.

As to mixing various wavelengths together is there no limit to how many you can cram together? Say I have a phot receptor 1mm square. Just how many wavelengths can I get on that target simultaneously? I huge number I bet but not infinite either I would think.

While we wait for some super-geek physics enthusiast to answer that, why not read my take on it?

The thing is this: An electromagnetic wave or signal is just that, a wave of some type, just like a soundwave or ocean wave. This can be represented like a function, like those that are drawn on a blackboard at school. Now here is the thing: those functions can be mathematically decomposed into a number of regular “sinusoidal” functions, each with a different frequency or “wavelength”. This means that they can be combined (summed up) to result in the original wave or function. This is mostly a mathematical issue. You can see that it is not a question of “how many wavelengths you can fit in a certain area”. It simply means that some waveforms can be represented as the sum of a number of other waveforms of different wavelengths. So you can represent a certain “light” waveform in two ways: you either plot the exact waveform of the light,… or you simply state the number of different sinusoidal waveforms of different wavelength that can be summed to form the original. The latter form is preffered because it’s easier, I think.

Now, … I wait for the phycisists to clobber me. :smiley: