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

How can we be sure that other people see colours as we do? I know I don't (big debate over whether friend's shirt was blue or purple- it was slightly lighter than the background in Classic Goo).
Also, who's a synaesthete? (i.e. every sense is linked to the others, so music sounds like colours and colours have sounds, tastes, etc.) I thought everyone saw things like this.
BLACK IS NOT A COLOUR.
Neither is white.
They are, respectively, a hue and a tint.
Any takers?

I am colourblind but never noticed this until it was tested with those spot test things. I am not conscious of any missing part of my range but there must be...so therefore my perception of colour must be different from yours.

Is it red/green colourblindness?

Yup - approximately 25% of males have noticeable (by doctors and scientists) Red/Green colourblindness.

Does it mean that you cannot distinguish between the two colours? For example, you know that grass is green, but does it look the same as a tomato? And do you actually see any other discernible colour instead?
Forgive me if I'm asking daft questions, but I've not had the opportunity before.

No - I can always tell a tomato red from a grass green. Where it gets tricky is when two colours are the same temperature and one is greeny and the other is reddish. Particualrily brown - I can't tell a greeny brown from a reddish brown. Fortunately the need to do so is rare (outside of cricket stain analysis) so I really never noticed until I was about 15, and since then only occaisionally.

I like your use of 'temperature' to describe colours. Maybe you compensate by having better perception of the qualities of colours, in a synaesthetic way.

Also I have seen people playing snooker, or pool, or whatever, pot the brown thinking it was a red.

Now that WOULD be annoying

a*cB

Hello again (did you get my e-mail?)
I think I see colours brighter than other people- something that they swear blind is beige, I perceive as orange.

(Yes I did, thanks, sorry I didn't reply, I'll be in touch when I know what I am doing later this month).

Women actually tend to have more detailed colour perception than men. So women will see aqua, and jade, and turquoise, where men will see bluey-green.

Different colour perceptions is the only possible excuse for the way some people dress.



a*cB

"Temperature" is an art term used in colurs that is purely a perception that the more yellowy or red a colour is the warmer it seems to be. Thus to paint a green hill with shadow and sunlight you add a bit of yellow where the sun is (warming it up) and a bit of blue for the shadow (cooling it down). This is also why oil painters avoid using black because the pigment that makes black has a lot of red in it and so can make shadows seem unnaturally warm.

Greetings fellow artist.
I avoid using black for shadows or darker shades because it makes them dirty, rather than the darkening you get if you use their opposite.
As for some people's dress, I knew someone who would only dress in black (a Mock-Goth, unfortunately). However, since black is NOT A COLOUR but the darkest, dimmest hue it is possible to get, she wore different colours of black. She never seemed to notice but it looked terrible, especially with red-black and blue-black.
Ability to perceive nuances (lovely word!) of colours is great, but can go too far; what person uses the words 'taupe' or 'ecru' in general life?

Colour temperature is a scientific thing. Can't temember the exact definition - something to do with bloack bodies and raising the temperature of them. For example average noon daylight (in temerate regions) is about 5500K.

Scientific temperature unfortunately is the complete opposite of an artist's idea of temperature here. It is based on the fact that very hot things glow with a particular colour. (Relatively) cool things glow red, hotter things glow orange, hotter still is yellow and so on up the spectrum to the blue glow of a blue star, the hottest thing in the visible spectrum. Artists think the other way around, with blue as the coldest and red as the hottest (think ice blue vs fire red).

The human eye contains three different types of colour sensor as well as a brightness sensor. These three are tuned to red, green and deep blue. The blue sensors are much sparser, which explains why blue lights often look blurred. Any one of these three sensors can be missing in a colour blind person, or any combination. The most common deficit is one of the red/green pair (I can't remember which). This is much more common in men than women. I think 1 in 10 men, 1 in 100 women or something like that. Many men live their lives never knowing that they are colour blind.

If you have all three sensors, then the chances are that you see colour in the same way as everyone else.

But does this arrangement vary individually? You wouldn't see a colour as being exactly the same as another person would; sometimes they have very different ideas of what colour something is.

But is that due to how your brain interprets the different signals sent along the optic nerve?

Gnomon you are correct in saying that while the actual colour temperature gets hotter, the colour of the light is refered to as cooler

Yes, that's probably the reason.
I see temperature in the artistic sense as based on the 'mood' of the colour.
Blue, for example, is a 'cold' colour but those approaching red (like this background) are more 'welcoming' than most. I hope that doesn't sound too drippy.

There are a number of stages here which are roughly: input (light entering the eye), reaction (cones 'fire' in resonse to this light), composition (the messages from different cones are analysed together) and perception (the result of this analysis is classified).

Nearly everyone's input is pretty much the same i.e. a single light source will reach the back of my eye in pretty much the same state as it will reach the back of your eye.
The reaction varies from person to person because the tuning of the cones varies from person to person (and in real colour blindness cases some cones are absent/innefectual) and varies according to an individuals temperature and blood sugar levels etc.
Composition, again, seems to vary from person to person. Some people pick up smaller regions of colour difference than others who see the whole as a single block opf colour.
However, perception seems to be a fairly crude affair and one which is learnt so the same light source can reach our eyses, our cones react somewhat differently to it, our composition can be different yet at the end of it all we both decide that the light is, in fact red. (Whether we are likely to just ignore it anyway is proportional to how near we are to the drivers seat oif a Dublion taxi )

Scientists, particularly astrophysicists, use the term hot for blue and cool for red, based on the colour temperature. Photographers measure colour temperature of incident light with a meter, but I don't know whether they use the terms hot and cold. Artists definitely use the terms warm and cool, warm colours being at the red (scientifically cold) end of the spectrum and cool colours being at the blue (scientifically hot) end of the spectrum.

Photographers use the terms warm and cool the same way artists do (a warming filter eg wrattan 81series is a yellow/amber colour).