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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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This note was uploaded on 03/07/2011 for the course PSYCH 120B taught by Professor Shams during the Winter '09 term at UCLA.
- Winter '09