The loss of violet

[steuard]

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 discussionPurple, as you no doubt recall, is a compound color: it's what we perceive when we

Comments

[nemene]

had you found that link first, sorry, was in a rush but you had peaked my interest and that was what I found...

I am having trouble finding a good reference for this but an interesting coincidence from what I have seen before is the depth of color penetration in water. Red penetrates the least, blue the most. The coincidence is that from some graph a I remember seeing it made it lok like the color wheel was real... the penetration of orange was ~average(red, yellow) and the penetration of green was ~average(blue, yellow) which makes sense as a near linearization of the response curve. The coincidence is that because penetration depth drops off for shorter wavelengths then blue the penetration depth of violet is ~average(blue,red). The last one may have been less close then the others, but it was close enough that I simply dismissed it as the expect behavior given violet is blue plus red, false premise, strangely accurate result...

Complete speculation, but it occurs to me to wonder if this symmetric characteristic of the penetration depth has any relationship to why we would have the secondary red perception bump, causing violet to be perceived as purple. I have no idea what the causal chain would be, but if violet light behaves under enough natural conditions in a fashion similar to red mixed with blue it would then fit for this otherwise odd feature.