An Introduction to Colour

The human eye is a very clever piece of apparatus. Its operation is relatively simple, but the reason behind its design is difficult to fit in with natural evolution. It is the one part of the human body that in evolutionary terms does not appear to give any major survival advantage. The human eye seems to be more advanced than the eye of most other creatures on earth, but is less perceptive than most birds of prey and many animals. What is this major evolutionary difference? Study indicates that the only real advanced feature of the human eye is the detail perception ability.

Colour perception. Does it have survival advantages? Do you get any extra information from watching a film in colour rather than an old black and white film? No, apart from the colour. When I was growing up, there was no colour television, most films were in black and white, most of the outside world was covered by soot and grime and most peoples attire was dark and, by today’s standards, depressing. I led a very active childhood, much of it spent outdoors climbing trees, building rafts, tickling trout, bird watching, fighting, hiking, cycling, camping, etc., etc.

During my lifetime I cannot bring to mind a single instance when my colour perception gave me any significant advantage over any other creature. I had sufficient artistic talent to go to the Bolton College of Art, and whilst there I was given colour tests which rated me as having 100% colour perception, so I wasn’t deprived of any colour ability. Oddly enough most artists have a degree of colour blindness, mostly Red/Green, and many have quite severe colour blindness. What is more curious is that in general, the more severe it is the better the colour handling of the artist.This could indicate that ‘colour blind ‘ people have a more advanced colour perception than ‘normal’ people. This could also explain why other creatures have a better general perception than humans, in that they can see more colours than we do. My argument, (And most of the evidence) indicates that the human eye can only perceive 4 primary colours, White, Yellow, Red and Blue. It is possible that other creatures can see far more ‘Primary’ colours than we can, which would give them a far greater survival advantage.

In general, my argument is that colour perception is a biological device in which a brain (Any type of brain) divides the received energy  of light into a certain number of ranges, the number depending on the needs of the particular creature. This division is handled by the ‘rods’ and ‘cones’ of the eye in humans, but many creatures only have ‘rod’ type receptors. This does not mean that these creatures can only see in shades of grey, they may be  able to see (say) 20 primary colours, which to them are as distinctive as Yellow and Red are to us. It is the individual brain that allocates a sensation to any division of light energy. To a bird of prey the emitted energy  from the body of a mouse may give the same sensation that we get when we see the colour Red.

As an engineer I have a natural curiosity to find out how things work, and why they work. The following pages derive from my curiosity about colour blindness.

One of the problems with colour is the large range of colour names. If I say Blue is it Prussian Blue, Azure Blue, Royal Blue, Indigo etc.? If I say Red is it Blood Red, Carmine, etc.? If I say Yellow is it Daffodil, Lemon, etc.? There can be only one primary Yellow, one primary Red and One primary Blue colour, an obvious problem never considered by the physicists.

All the colour posts are just as important as each other, and in reading them in isolation you lose the build up required to grasp what it is about, (like starting a book at chapter 8).   For best results, the following order should be followed: –

1. An Introduction to Colour.
2. Colour and the Prism
3. The Origin of Colour
4. Newton’s Colour Wheel
5. Light Passing Through a Dense Medium.
6. Energy of Coloured Light.
7. Colour Filters
8. Projected Light
9. The Taper Slit Experiment.
10. The Taper Silhouette Experiment.
11. Colour Test Bars.

Note: I am quite happy to answer technical questions relating to colour, subject to both question and answer being published on this web site.

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