How Do We Perceive Colour

The meaning of colour is very complex to describe. When people try to describe a colour, they usually link it with something of that colour and give an example to explain it. For example, the colour "Green" is linked to grass or trees since these have in common the green colour.

However, there is evidence showing that some cultures do not list colours in the same groups other cultures do. For instance, people from Berimno separate "green" into two sections: nol and wor (Davidoff, Davies, and Roberson 1999).They cannot distinguish blue from green, but this is good in some way because it is not difficult for them to perceive "blue "as being "green "as they are found in the identical colour group (cited in Perception book, Fifth edition, chapter 7, page 235). Bornstein and colleagues carried out a research in order to find out whether there is a difference between the way infants and adults perceive colour. Firstly, they showed a bit of light, whose leading wavelength was 480 nanometres, a light that is familiar to blue. After looking at the light for some time, infants showed there incapability of seeing the colour.

Bornstein then used a new bit of light that was similar to the previous one with wavelength 450 or 510 nanometres. The human eye perceives that light as green. Infants responded to the light this time unlike before. The results of the experiment showed that both infants and adults perceive colour in the same way (cited in Perception book, Fifth edition, chapter 7, pages 235-236).

Isaak Newton argues that objects are not coloured but are given their colour through the reflection of light from certain parts of the scope.Moreover, there are some people who see colours differently from the majority of people because they may have irregular eyes or irregular brains and these are the two important parts from where people perceive colours. Newton discovered that the light which showed up as orange was metameric with a combination of red and yellow lights. By looking at Newton's colour circle, you notice how he expresses his ideas from the results of light combinations. His circle is separated into seven different colours: yellow, green, blue, indigo, violet, red and orange.The false belief that there are only seven separate pure colours, leads to false predictions of some mixtures.

Therefore, Newton's colour circle should not have confines which divide the circle into these separate colours (cited in Perception book, Fifth edition, chapter 7, pages 236,240-242). Colours contain three types of virtues and those are: hue, brightness and saturation. The first one, which is hue, does not have the same meaning with colour and it can be referred when people want to distinguish the hues of a colourful T-shirt.There are two different expressions of brightness. The first one is when people want to describe the light coming from a star by using the word brightness but when they want to express the light of a surface they use the term lightness.

An example of saturation is when after washing a pair of trousers many times you can see that the colour is not the same as it was when you were first bought it, it becomes pale (cited in Perception book, Fifth edition, chapter 7, page 237).There is color constancy when there is no change to an objects color as there are changes in the band of light leading to have changes in the light reflects toward the viewer from object" (Jameson and Hurvich, 1989, page 245). However, univariance principle is the theory in which one variable can be corresponded by any photoreceptor reply that the quantity of light is occupied, and this happens because there is no information about the amount of wavelength of the engrossed light (Naka and Rushton, 1966). People or animals that have only one cone pigment and cannot distinguish one colour from a different one are called monochromatic.

Furthermore, the term dichromatic is given to those who have two cone pigments and are more likely to have colour confusions. People or animals that contain three cone types of photopigments are called trichromatic and this is what the human eye consists of. This means that each photopigment gets responses from three dissimilar wavelengths (cited in Perception book, Fifth edition, chapter 7, pages 247-250). The three cone types are the short-wavelength responsive (S cones), the medium-wavelength responsive (M cones) and the last type is the long-wavelength responsive (L cones).

The quantity of light which is being engrossed by photopigments is measured by the microspectrophotometry. It is separated into four sections: micro which means little, spectro shows the range and the word photometry means: mensuration (metron) of light (photo). The cone pigments consist of a membrane protein which is artificial with vitamin A and linked to retina. The development of photopigments is depended by the genetic orders that DNA gives. However, S cones can be found in the fovea of the retina, a place where L and M cones can not be found.Moreover, another difference between the three cones is that the shape of S cones is different? in contrast ?? the other two cones (Rodieck, 1998).

A study from Roorda and Williams (1999) was undertaken in order to find out the differences between the three cones. Their findings showed that less amount of S cones were abnormally spread among a big amount of M and L cones. Furthermore, the place where the L and M cones were abnormally spread was the mosaic of cone photoreceptors (cited in Perception book, Fifth edition, chapter 7, pages 251-252).Achromatic and chromatic channels are channels which get signals from the three cone types.

There is one achromatic and two chromatic channels. To produce an achromatic channel you should estimate the sum of L and M cones. This colour appears white. Furthermore, the blue and the yellow channels appear when the sum of the M and L cones are deducted by the S cones.

Additionally, the differentiation between M and L cones give the red-green channel (cited in Perception book, Fifth edition, chapter 7, pages 256-258). What is more, the three cone types match with the three neurons of lateral geniculate nucleus.The M cells are the magnocelluar neurons, the K cells are the koniocelluar neurons and the P cells which are the parvocellular neurons (cited in Perception book, Fifth edition, chapter 7, page 258). DeValois through his investigation on monkeys LGN cells whose vision is like ours, displayed dissimilar groups of cells. There are two types: the opponent type and the nonoponent type. Nonoponent cells convey their response by increasing the action of ON cells causing all wavelengths to produce an ON reaction.

In the same way, when there is a decrease in action by other OFF cells, all wavelengths produce an OFF reaction from the nonoponent cells.When there is a response from both cells this leads to having an achromatic channel. Moreover, in the opponent type there is either an ON or OFF reaction it is not possible to have both of them, and the wavelength of light has an important role for the responses of the opponent cells. For example, a long- wavelength means an ON reaction, a short-wavelength means an OFF reaction. If there is a possibility to have both of them the reaction which is given is minor. However, if the one side of the range gives an ON reaction and the other side an OFF reaction there is an ON to OFF reaction.

The opponent cells are separated at the green and red part. Furthermore, when there is a contrast between L and M cones, neurons are given the name M-L cells, and when S cones are in contrast to M and L cones the cells are called S-(M+L) cells (cited in Perception book, Fifth edition, chapter 7, page 259). To conclude, colour perception plays an important role in the way people perceive things. The existence of wavelengths and light which are absorbed by photo pigments are those which give colour to an object. People think that the concept of colour is very simple but there is a deeper explanation to describing what colour actually is.