h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

I read somewhere that there is a rare condition in which women [never men, just women] have an extra red receptor in their eyes. These lucky women can perceive differences in shades of red that people without the extra receptor can't perceive.

While I hope philosophy has moved on a bit since 1738, I think the point is still well-taken: what goes on in the mind is not purely objective physics, but the interpretation of that physical reality according to the informational needs of the end-user there.

What Konrad Lorenz, who was both a biologist and a Neo-Kantian philosopher (he held the chair at Koenigsburg, when Koenigsburg had a chair, or even a town to put one in) called 'hypothetical realism'.

My point being, NOT that it isn't true that 'light is X, and we can measure it, and those are the Rules, and the Rules are Good'. Of course all that's true. But as your TED Talks video showed, the process of perception - and the evolutionary path it took to get there - is also a fruitful area of inquiry. Like what Paulh said about women who can see more kinds of red.

How did that happen? Why? What good is it? Is it useful, or is it just for lagniappe?

People in some hunter-gatherer cultures see colour differently, I'm told. I still harbour the suspicion that people in other millennia may have done the same. How much of our interpretation of colour is biological, how much cultural?

I agree. It just gets my goat a bit when some people try to make out that just because our visual system (amongst others) has a bunch of short-cuts, patches and workarounds in it that mean we don't perceive reality quite as you might expect, that that means that there IS NO objective reality and EVERYTHING is about our perception of it.

I agree. Those people have been reading too much Lacan, and reading it while watching TV, probably.

= Epiphenomenon

Hoo, I get your frustration with the everything is subjective crowd, but actually I think it makes better sense to say that colour is subjective and that the frequency composition of light is objective. The example of brown and orange show that: their frequency compositions are identical, what makes us perceive it as brown or orange is the context, i.e. the rest of the visual scene, yet still they are clearly different colours.

The same is even more true of pitch. Pitch is straightforward for pure tones at a certain frequency, but it's still a very active area of research even to try to define what pitch means. The answer seems to be that there isn't even a consistent and general meaning.

Other color vision anomalies, one affecting people from Ulster more frequently than those from the remainder of Ireland, is a type that makes it difficult to distinguish colors of the same hue, but differing saturation.

This particular color vision problem can sometimes be overcome by means of training by a trainer who can readily distinguish the differences in saturation.

Also, there's a mutation affecting about 10% of the total population affecting transparency of the membranes and humors of the eye, so that people who have it can see an entire octave or more into the infrared* and one chromatic hue in the ultraviolet.

This is seen on the night vision rods and and anybody with normal night vision can see in this range, even if they haven't the transparency mutation, if, for example, they have a cataract operation and the natural lens is replaced with a quartz glass lens.




*The ashen light, so called, since one of the traditional sources is a hearth in which the last red ember has died, after which one closes one's eyes for a minute or so and then may be able to see a faint pallid white coming from the hearth.

Things which are charcoal black indigo blue (the color of blue jeans) will appear a pallid white in the ashen light since those two colors are in octave relationship to the ashen light, same principle as things illuminated in light of their own hue appear white.

The dark side of the crescent Venus radiates in the ashen light, but must be viewed through a quartz glass lense to be visible, since ordinary glass is opaque in the near infra-red.

Double or halve the wavelength and that makes an octave, so red light at 700 nanometers is in an octave relationship to violet light at 350 nm, ordinarily considered the limits of normal color vision.

The cut off for the ashen light is around 1500 nm.




Chromatic hues corresponding to the black keys on the keyboard are about 50 nm apart, the warm colors triad, red, orange, blue, the spring green (or yellow-green) and forest green (or blue-green) doublet, the blues triad, cyan(the color of a clear blue sky), indigo and violet.

Fill in chromatic hues between, corresponding to the white keys, and that gives you 22 chromatic hues between the extremes of the normal visual spectrum.

Finer differentiations are possible, for example, 22 distinct hues between yellow and green, with smaller numbers between other pairs of adjacent 'black keys', so to speak.

>> frequency composition of light is objective <<

The same light particle may be measured to have any "frequency". To one observer it might appear red to another it might appear blue.

For technical determinations of wavelength and frequency, the source and observer are supposed to be at rest with respect to one another and reasonably close together.

For purposes like radar and lidar, determinations are made by examination of electromagnetic radiation reflected back to the source from the object under study and differences in wavelength and frequency presumed to be due to differences in state of motion.

There's a technical rule that things smaller than the wavelength being used for the study cannot be imaged in that wavelength, so if its radar in the 10 centimeter band being used for studies of objects in orbit around the earth, things much smaller than a softball cannot be seen.

On the other hand, say there's a problem of dust obscuring objects in the background, the dust can be made to disappear by means of using a wavelength greater in size than the obscuring dust particles, at least so long as it does not induce a resonant fluorescence in the dusty medium.

There's a wealth of detailed explanation in this thread, more than I can really understand.

My mothers father was colorblind. I had two uncles who were colorblind. My mother and her sister were carriers. The sister had four sons, none of them colorblind. That left my mother, who hoped she wasn't a carrier for colorblindness. I turned out okay, and my brother seemed okay at first. Later in life, a sophisticated test showed that he had some colorblindness. This also meant that my sister might be a carrier, but her two sons were normal....

...my own two eyes don't match exactly in color, color vision or acuity...

...despite an unfortunate anti-semitic remark he made in it, Goethe's color theory covers a lot of ground most authors never do.

His remarks on colored shadows, for example, are susceptible to application in shadow puppet stage craft...

I'd seen the effect, colored shadows, in outdoor street lighting at one of my stepfather's favorite bar and grill establishments and already knew how to produce the effect before I read Goethe's material on it.

It appears that some people actually know a thing or two
about colour and perception. I have to admit several posts
left me scratching my head for my lack of understanding of
the science involved but they were posted with such great
conviction they must be Truly informed or well plagiarised.

The colour red seems to have enjoyed some extra discussion,
especially in regards to it not actually being seen equally
by all species or genders.

This raises a few questions.

Blood? Do we have particularly evolved responses to it?
And then by association to any red object?

Bulls? The popular understanding is that bulls 'see red'.
But I have heard that they are mainly colour blind and
are just reacting to the fluttering of the bullfighters cape
as it is percieved as a rippling muscle reflex often seen
in the shoulders of predators as they prepare to charge.

Flags? I did say that Part Three of this thread would be
an analysis of the cause/effect of colours in specific
national flags. Japan and Canada for example are both
red and white - blood on the snow.


~jwf~

There's a popular misconception that dogs are color blind. They are not really, but their vision is much stronger in the warm colors than it is in the cool colors.

I've seen it reported in the New Scientist that dogs have black-and-white vision. The only reason they could tell the red ball from the green ball in tests was because they can smell the difference in the paints.

I've always intended to write a series of Entries on Colour Vision, but the subject is rather huge.

If you're taking on colour problems, you might want to look at Oliver Sacks' study on the people of Pingelap, called 'The Island of the Colourblind':

http://serendip.brynmawr.edu/biology/b103/f01/web3/wise.html

Another interesting oddity is what makes people look the colour they do to other people. We're all aware of the melanin differences that create the idea of 'black' and 'white' people - or, where I come from, 'fish-belly white' - but have you ever seen a blue person?

If you lived near Troublesome Creek in Kentucky, you could easily run across one: The Fugate family have hereditary methemoglobinemia, a condition previously found among the Inuit.

http://www.indiana.edu/~oso/lessons/Blues/TheBlues.htm

By the way, the temporary 'cure' for this condition is to take methylene blue pills.

Last night, I caught the very end of this programme about research into unconscious vision, and was fascinated: http://www.rtve.es/television/redes/ (In Spanish).

Beatrice de Gelder on 'blindsight': http://beatricedegelder.com/documents/Uncannysightintheblind.pdf (In English)

Is it possible to see something without knowing you can see it? Video: http://blogs.scientificamerican.com/observations/2010/04/22/blindsight-seeing-without-knowing-it/

When my mother was in college I used to read her textbooks. One of the books on linguistics had some interesting stuff about colour terms. Some languages have only two: light and dark. Some have three: black, white, and red. (No language has black, white, and blue: it's always red.) There are no languages with four colour terms: the next step up is five (I think it's blue and green that are added, but I can't recall).

TRiG.