Re^2: How many colors does a rainbow have?

By that token maybe 4, because we also have separate receptors for brightness?

Oh, and I've heard there are people with some mutations who have pigments for two different shades of red, so they can actually see RRGB+brightness.

Comment on Re^2: How many colors does a rainbow have?

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Re^3: How many colors does a rainbow have? by ikegami (Patriarch) on Jan 25, 2009 at 20:48 UTC
Such people are called tetrachromats	[reply]
Re^3: How many colors does a rainbow have? by BrowserUk (Patriarch) on Jan 25, 2009 at 23:10 UTC
By that token maybe 4, because we also have separate receptors for brightness? I don't think that you can classify intensity as a fourth "color". If you increased the intensity of the spectural components in the rainbow whilst leaving their ratios unchanged, the observer would tend to squint, closing the iris, to reduce the overall amount light (number of photons), reaching the retina, with the result that the observer would perceive the same information. Besides which, the rods only tend to come into play in low-intensity situations, when color information becomes distorted anyway. For example, at night, the green leaves of a rose tend to appear brighter than the red of the petals. Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error. "Science is about questioning the status quo. Questioning authority". In the absence of evidence, opinion is indistinguishable from prejudice. "Too many [] have been sedated by an oppressive environment of political correctness and risk aversion."	[reply]