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August 20th, 2012

steuard: (Default)
Monday, August 20th, 2012 10:13 am
I was thinking about color this morning (yes, I do these things), and I was struck by a disturbing thought: when did I last see violet? Not purple, which I see all the time, but actual violet. [I'm not the first person to wonder this: here's a very thorough discussion.]

Purple, as you no doubt recall, is a compound color: it's what we perceive when we see a mixture of red and blue light. But violet is a pure color: light with wavelength somewhere a little over 400nm. (Side question: anyone have a clue as to why purple and violet are perceptually similar?) So what's the problem? RGB monitors, that's what. The shortest wavelength of light produced by an RGB monitor is blue, which is probably around 460nm or so. That means that your monitor is incapable of producing a violet color. Looking at a picture of a rainbow on your computer screen is inevitably a less vibrant experience than seeing one in person.

So, fine, look at a printed photograph. Well... not so fast. I don't know how all the different types of photo printing work, but a lot of printers are RGB or CMY themselves (and I think that CMY has the same problems as RGB in this regard, or worse). I have no idea what the process is (or was) for traditional photo printing from the analog era, but I'm willing to imagine that there are photo printers today who are capable of printing with actual violet dyes. But wait: what sort of camera took the photograph? Again, I don't know how good traditional film cameras were at capturing violet, but today's digital cameras are (as far as I know) also RGB.

So: when did you last see violet? Think back: what does it look like?