Canuke said:
I think you answered your own question; lemon yellow isn't monochrome, but is a broadband of colors (somebody should get one of those Nichia phosphor lemon-yellows to Craig for a spectrum).
In my experience, monochromatic amber does blend into mono-green without ever getting to "lemon" yellow... ever since I saw the phosphor-based yellow (in a Brookstone keychain light; as much as I liked that color, $20 was too steep), I realized somehow that it wasn't monochromatic, and no monochromatic yellow ever looks like that.
Until I can get my hands on a range of monochromatic yellow LED's and one of those phosphor ones for comparison, I couldn't say exactly what looks different... just that it does.
I also wonder whether nobody really wants to make bright LED's in the 535-570nm range. For some reason, people -- myself included -- seem to think that yellow-green is the least appealing monochrome color.
If 570 is the highest yellow green and 590 is the typical amber, then wouldn't the upper 570's and 580's range be a pure, lemon yellow, while still being monochromatic? I notice that there doesn't seem to be anything ever marked in that range. I myself was wondering what was holding them up from producing LED's in that range.
I would imagine the yellow phosphor LED's would look something like yellow neon, and that is more saturated than incandescent yellows, but still pale compared to monochromatic LED's. (Brookstone has those in keychains now? I'll have to check that out. The only place I may have ever seen those before is in those cellphone antennas they often have displayed in store windows, and again, it was very pale, and blue was visible in it).
One really saturated pure yellow I see is the background color for some 1990's single color LCD signs I see on some transit vehicles. (though that industry has now gone solidly with amber/orange LED's, now). The color (roughly the hue of "lemon yellow", but much deeper; perhaps like a "sun yellow", but of course not literal sunlight) seems to be from a filtering of white flourescent light (you can see the white along the edges of the filter), though, but I always imagined that was what would lie between the color of the yellow green LED's and the amber LED's and low pressure sodiums. The yellow-geen does look almost like lemon yellow when you look at it long enough (especially at the die), and when you look at red for a long time, until the red itself looks almost like amber, and then look at the amber LED's or LPS's, they for a while look like an almost greenish lemon yellow!
