Overanalyzed

Colors

September 30, 2008 at 5:13 pm | In Science, Technology | No Comments
by Chris Davenport

Purple is an odd concept.

We see it as a combination of red and blue… because we have roughly RGB retinas… but then we see 50%R 50%G as yellow, when there’s a real yellow that just triggers 50%R 50%G.. We can’t see the difference though.

But there’s no frequency of light that corresponds to purple. Makes the color wheels seem a little goofy, honestly. And suddenly bothers me to find purple on manmade rainbows, when real rainbows have indigo and violet, neither of which have any red in them.

EDIT: I recently discovered that the red cones in your eye actually do have a second peak in their response to color. Instead of a nice bell curve centered around red, it tails off more slowly in the high-frequency (green/blue) direction, and has a second, much lower hump above blue. This is why some people may see some purplish colors there, it’s signal confusion.

Violet is past blue.. past indigo.. ultra indigo… Eyes don’t work at the ultraviolet frequencies. As you move your view across a rainbow, the light goes from yellow to green to blue, then it goes more blue to indigo, then to violet, and then disappears as it gets beyond our range of vision.

There’s no purple at the high edge of a rainbow. There’s no red color there. Purple is the mix of red and blue light, and it just doesn’t exist as a physical color, the way white and black don’t. All the other colors on the wheel, sure, but there are no purples, no colors that mix red and blue. Just like there are no numbers >5 and <-5.

Even the wikipedia article indicates that they’re showing some electric violet color in which they’ve just added some red because violet can’t actually be represented in RGB channels.

In the photo, you’ll see some “purple” near the prism in the blue/indigo areas, which is a result of white light bleeding into those areas, the other colors have been lightened as well, to the point where the yellow is white as you get close. But it’s down near the bottom where you’ll see the blue just taper off. Red has a sharper line because cameras have lenses that aren’t transparent to red-infrared.

Obviously our artist has an issue with the whole blue-to-violet range, he’s clearly indicated a cyan color as blue.

RGB is a total scam. We lost our indigoes and violets, and have to put up with this sham of purple instead. There was a time that 0,0,255 would have been called violet, because blue was/is 0,128,128.

The whole lower right quadrant is colors that don’t exist. Notice how they’ve compressed the blue range so that the 3 first tier colors (Blue/indigo/violet) fit in 30 degrees, compressed the orange section so it’s 2nd tier, elongating the greens to invent cyan. ROYGBIV man. Not RYGCBM.

It’s not unreasonable. People are most sensitive to greens, less so to blues, least to reds. Any division that looks balanced to us would have to be biased. And we have a way to identify red+blue and red+blue+green individually, so we might as well put them on the wheel even if there’s no such thing.