Re: CHAT: Indigo (was: Orange)

On Wed, 5 Jun 2002 23:35:24 +0100, Tim May <butsuri@...> wrote:
>
>I'm no expert on the matter, and I'm going to look into it further,
>but...
>
>In reality, yes, visible light is a spectrum stretching from red to
>violet.  But that's not how we really perceive it - what our brains
>get is a varying level of excitation of three types of cones* in the
>retina, which peak at different wavelengths**.  So human perception of
>colour is more like one of those triangles we were talking about
>earlier when we were trying to classify conlangs.  This perhaps is
>related with the idea that purple (red plus blue) is similar to violet
>(a shorter wavelength than blue).
>
>There's a technique - I forget the details, but you can create the
>perception of any shade of colour by means of two monochromatic
>sources.  Or something like that.  I think the inventor of the
>Polaroid camera was involved.  I need to check my notes.
That's about what I remember. A quick look gives Edwin H. Land. IIRC, his
results were an improvement over the color triangle. I'd have to read
carefully to come up with the specific answer. One article was in
Scientific American, May, 1959.

Jeff J.

>*  Which is the English name for the photosensitive cells in the retina
>   used to perceive colour.  I know Nik just answered this, but I was
>   already writing.  The name distinguishes them from rods, which are
>   more photosynthesis but cannot perceive color.  The cones are
>   concentrated in the fovea centralis, in the center of the visual
>   field, which explains why a)  if you suppress the saccadic motion of
>                                 your eyes, your peripheral vision will
>                                 lose colour
>                             b)  you can see dim objects (like stars)
>                                 better with peripheral vision, which
>                                 is mostly rods.
>
>** I have notes from a neurophysics course around here somewhere,
>   which will tell me exactly what the peaks are.  I'll post it
>   tomorrow, unless somone else has found it in the meantime.  They
>   aren't as evenly spaced as you might think.