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Unformatted text preview: 24 th January 2011 Psych 120B Lecture 5 Perceiving Colour I. Basic Concepts I I. Some Colour Phenomena I I I. How does colour experience relate to wavelength? IV. Basic Mechanisms V. General Theories of Colour Vision VI. Colour constancy, reflectance, adaptation Basic Concepts Physics o Colour of a surface is determined by light reflected away by the surface. It is not something inherent to the object, unlike texture. Relevant dimensions of light influences what we perceive o Wavelength o Wavelength purity vs. broadband composition How much the wavelength is mixed with other wavelengths. Physics of Light White natural light o Has all visible wavelengths with equal contributions (broadband because it is a broad wavelength of light) Colour of a surface o Is the colour of light reflected away by the surface (the rest of light is absorbed) Basic Concepts Psychological Dimensions o Hue related to wavelength (relation is not simple) o Saturation relates to the purity or selectivity of hue (how much white is mixed in) o Brightness not confined to the experience of colour, even grey stimuli can be calculated by brightness. It is how much light you can see. Saturation Ex. Difference between red and pink .. and really really light pink o Pink is a less saturated version of red. The more white you add, the less saturated the colour is. Colour Picker in Adobe Photoshop Usually allow you to pick hues and then adjust the saturation (purity) and brightness....
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- Winter '09