Question
In his book The Photographer's Eye, photographer and author Michael Freeman says:
Another consideration is relative brightness. Different hues are perceived as having different light values, with yellow the brightest and violet the darkest. In other words, there is no such thing as a dark yellow, nor is there a light violet; instead, these colors become others — ochre, for example, or mauve.
Update: Freeman is clearly talking about something more serious than the labeling of colors. In The Photographer's Eye, the above quote is part of a relatively small section, but the same concept occurs throughout an earlier book of his, Mastering Color Digital Photography. The idea seems to be that when darkened, yellow loses the essential qualities that make it yellow, and when made bright violet loses the essential qualities that make it violet — in a way that red or blue do not. These qualities are clearly more than their position in a color space, and they're also clearly more than the name applied.
My earlier discussion (the next few paragraphs) was about how I've seen this in practical effect, and how I think you probably can too if you haven't thought about it before. But the question I still have is why?
Some of the answer may be cultural, but if it were entirely arbitrary, it seems odd that these particular effects would be claimed in reverse for colors which are direct contrasting colors on the color wheel. That seems to imply some technical reason beyond any sort of thing like "purple is royal because of the rareness of the dyes in ancient times."
And, particularly with yellow, I've seen this to be true. If you've ever worked with the 16-color VGA pallette, you know what I'm talking about — in fact, the HTML 4 spec names dark yellow "olive". I realize that the other colors have, well, colorful names (lime, for example) but who ever heard of a yellow olive? And this isn't something wacky with the restricted colors available — it's what you get when you take pure red and pure green mixed, and then cut the brightness in half. I don't think this is just a matter of naming — I remember being frustrated with the inability in a 16-color scheme to make a dark yellow that reads as yellow.
I assumed that this was basically due to a limitation of the RGB color model — that the color exists, but we just can't get to it in that way. (Edit: this appears to be true of violet, in a scientific sense; it can only be approximated with purple, which is a mix of red and blue. See this Wikipedia link provided by Evan Krall in the comments below. There's something called the Bezold–Brücke shift involved, which might be part of the answer to this question.) But Freeman suggests something more about our perception than about the color model.
What's going on here?
Postscript: my six-year old, on her own accord, sorted her markers by "how bright the colors are":
I think Goethe would be pleased.
Answer
I think it's a bit more than simply saying "we have other names for those colours." Yes, there is a cultural component. If English didn't have the word "pink" we may very well refer to a colour "light violet." Some languages don't even distinguish between blue and green. But I believe in the case of Yellow, that the way our brain interprets colour means that the very best we can do with "dark yellow" is call it "gold."
Think about describing colour with "-ish" for example. We can have a bluish-green, or an orangish-yellow, but imagine the color yellowish-blue. It doesn't exist. The same with greenish-red. (Scintillating colour-changing fabrics notwithstanding.)
The "pure" colours our eyes perceive and our brains interpret are yellow, blue, green, red, and possibly brown. (See opponent process theory.) Other colour names are cultural and variations on those. For example, orange is a reddish yellow or yellowish red, pink is a pale bluish-red, violet a reddish-blue. So we find it difficult to imagine a "dark yellow" because our eyes and brain are more likely to interpret it as a "dark desaturated green" or possibly a "greenish brown."
Check more discussion of this question.
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