Wednesday, 1 February 2012

Colour light versus Colour pigment

Questions:
   •  What does colour mean?
   •  Would we see the colour without light?
   •  When do you see a rainbow? Why?
   •  Do all the animals see the same colours? And what about people?

Light and Vision_____________________________________________________

     The Colour spectrum: The familiar colors of the rainbow in the spectrum – named using the Latin word for appearance or apparition by Isaac Newton in 1671 – include all those colors that are visible to the human eye. 
      The ability of the human eye to distinguish colours is based upon the varying sensitivity of different cells in the retina to light of different wavelengths. The colour that we see is the result of a part of the visible spectrum that is reflected. We see a red apple because only that part of the spectrum is reflected. Black occurs because all the colours of the spectrum are absorbed rather than being reflected.

     If one or more types of a person's colour-sensing cones are missing or less responsive than normal to incoming light, that person can distinguish fewer colours and is said to be colour deficient or colour blind.
 
B
A









On the left the colours of the rainbow as viewed by a person with no colour vision deficiencies.
On the right the colours of the rainbow as viewed by a person with Colour blindness.

COLOUR LIGHT__________________________________________________________
     Additive colour describes the situation where colour is created by mixing the visible light emitted from differently coloured light sources. The result when all three primaries are mixed is white. This occurs because all the colors of the spectrum are present in white light.


Computer monitors and televisions are the most common form of additive light

COLOUR PIGMENT________________________________________________________
    A subtractive colour model explains the mixing of paints, dyes, inks, and natural colorants to create a full range of colours, each caused by subtracting (that is, absorbing) some wavelengths of light and reflecting the others.



Subtractive colour is used in paints and pigments.

The truth about Colour, by Peter Turner
INCORRECT                                     CORRECT

                                        a) Artist's Colour Wheel,             c) 21st century
                                                    19th century

Exercises__________________________________________________________________
1. Comment the difference between Colour light and Colour pigment.

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