Welcome to the fourth discussion on the ‘Colours!‘. The topic is getting so exciting and I am very much enjoying it. I am sure you are enjoying the series too, aren’t you?
Before going ahead, let’s take a quick recap of the first three posts we talked earlier. In the first post, we talked about our relative sensory system, due to which we can see. In the second post we discussed how we ‘see’. How the light emitted from the source gets converted into a brain signal. And further in the third post we met Mr. Light, talked how the ‘Electro-Magnetic Radiations’ of different wavelengths are ‘seen’ as different colours to us. Now today, we will be taking the topic ahead.
So we now know that, our eyes has three types of ‘Cone’ cells that works as receptors of three wavelength rays. These three wavelengths are seen as ‘Red‘, ‘Green‘, and ‘Blueish‘ in colour. In our eye retina, the count of such cones is about 2,50,000. Means nearly 83,333 per colour. That’s really huge. The ‘Rod’ cells mainly work as the receptors of Gray-scale values. The cones require more light intensity to detect the colours better. If the source light is deem, then these cones gets less sensitive to detecting exact colour variations. That is why we can not see colours properly at night or in low light. Different animals or bird may have different combinations and variations of such cones and rods in their retina. We, the humans, have the three colour receptor system, hence humans are called ‘Trichromats’. By combination of these three colours, we see all other colours.
Lets imagine an apple. We see the apple as Red. But Why? Imagine a pure white light coming onto the apple. The light hits the surface, bounces off and reaches to our eyes. Then our brain says “OK! here I see an apple”. This is fine, but what about “red apple”? Here is the answer: The light hits the apple and bounces off, but not all the light gets reflected. Because of some chemical composition of the surface of the apple, most types of wavelengths are absorbed in it. Only red wavelengths are reflected off and eventually reach our eye. So our eye only sees red ones from the apple. And as usual the brain says “it is red”. Same thing happens with all different colours. The colours that we see are the reflected colours only and the remaining wavelengths are absorbed in the surface.
We talked earlier that this topic has two main aspects – the scientific and the artistic. There has always been a kind of battle between the two, since early days. The scientist’s approach to study the colours and mixing of colours, was much different then that of the artists. This study or science whatever we call it, is going on from 14th century. ‘Leonardo da Vinci’ also mentions about colour theory principles in his writings in 1490’s. Later in 1704, we get a very detailed study by ‘Sir Isaac Newton’ in his book ‘Opticks‘ on theory of colours. Since then the study began to widen and broaden in many aspects. As far as the mixing of colours goes, there were two distinct groups or systems. These systems talk about getting all colours from three primary colours. As the human eye has the three main cone cells for Red, green and blueish colours, the early scientific approach was to believe these three colours as the primary colours. By combining the red, green and blue we can get all shades of other colours. This is called the RGB colour model. If we put a ‘Red’ spot-light on a white wall and mixed it using an additional spot-light of ‘Green’, how will the wall look? It looks yellow!
(I am not going to put any picture or image here, today! I WANT YOU TO IMAGINE) 🙂
So we can say that adding Red and Green light, we get ‘Yellow’. In the same way we can add Red and Blue lights to get a Violet (or precisely the ‘Magenta’) shade. And when we add green and blue lights, we get a shade called the ‘Cyan’. Likewise we can add any combination of light shade to achieve variety of other colour shades.
On the other hand this mixing of colours fail if you actually mix two such shades of paints. If you add Red paint in Green, you get a very dark blackish colour, but definitely don’t get ‘Yellow’. So Artists never really considered the RBG colours as the primary colours. Most of the times it is completely opposite. In the earlier case Red + Green = Yellow. Means Green was a primary colour. But in case of paints Green is made by mixing Blue and Yellow. Green is a secondary colour. We can produce any shade from paints if we have ‘Red’, ‘Yellow’ and ‘Blue’ colours with us. So these became the artist’s primary colours. Which is called the ‘RYB’ colour model.
So now which one is true? The Scientific? Or the Artistic? This debate went on till early 19th century. Yes! Still pretty old debate, hmm? And finally, slowly the world (scientists and artists) began to resolve and evolve the ‘Theory of Colours’. World’s current understanding about colours and its behaviour is very broad and deep. Both the above mentioned models are true. Yes both are true. They are just parts of the same system. They are not contrary to each others.
The first one, the RBG model, is called the ‘Additive mixing of colours’. This mixing happens when ‘lights’ of two colours are mixed. When brain receives signals of both colours, it dose the mixing job. The brain tells about the resultant colour. The second type is called ‘Subtractive colour mixing’. This happens when ‘Pigments’ of two colours are mixed. The pigment is the chemical due to which a paint has its particular colour. When one pigment is mixed with the other coloured pigment, some of the wavelengths are absorbed, because of the newly generated chemical composition. Hence, our brain gets different type of wavelength signal. Naturally, we ‘see’ different colour.
Now a days the painting technology and chemistry has became so advanced that we can produce almost any visible colour shade in paint. Many new colour models have evolved for better flexibility to particular sectors. For example, the screen you are looking at right now, the monitor, is completely based on ‘RGB’ colour model. The LDC contains three small coloured points for each pixel. The three points emit Red, Green and Blue lights. By turning the red and the green lights at the same time, our brain receives both the wavelengths signals and gets confused. And we call that newly seen colour, the yellow. Likewise we see all colours in the screen. It is just mixture and combination of the three main colours. The white is produced by turning all light point on and the black by turning off all.
The printing industry however runs on a very different colour model. It is called the ‘CMYK’ model. You must have heard it. Right? Here the paper itself is used to produce white colour. Then the three primary colours are ‘Cyan‘, ‘Magenta‘, ‘Yellow‘ and the ‘Black‘. The K stands for key and represents black colour. If Cyan is printed along with Magenta on a paper, it looks like Blue. Likewise we can produce any shade in printing. The black is used to darken the colours. This is also called the ‘4 colour printing’.
So we talked about the mixing of colours. I think that’s enough for today. I hope you enjoyed it. We will surely continue the discussion in the next post. Please let me know your suggestions or comments. Tell me how do you feel, Colourful? or not?