CMU CS 15463 - Light & Color (5 pages)

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Light & Color



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Light & Color

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Pages:
5
School:
Carnegie Mellon University
Course:
Cs 15463 - Computational Photography
Computational Photography Documents

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Light Color OUTLINE Physics Perception Color Reproduction Physics of Light and Color It all comes from electromagnetic EM radiation The amplitude of radiation is a function of wavelength Frequency 2 EM spectrum radio infrared visible ultraviolet x ray gamma ray long wavelength short wavelength low frequency high frequency Don t confuse EM spectrum with spectrum of signal in signal image processing they re usually conceptually distinct Likewise don t confuse spectral wavelength frequency of EM spectrum with spatial wavelength frequency in image processing Notes 14 Computer Graphics 2 15 463 1 Perception of Light and Color 1 Light is EM radiation that is visible to the human eye Wavelength range of visible band approx 400 700 nanometers We re most sensitive to greens yellows not very sens to blue Humans have evolved to sense the dominant wavelengths emitted by the sun space aliens have presumably evolved differently In low light we perceive primarily with rods in the retina which have broad spectral sensitivity at night you can t see color Rods have relatively good spatial resolution in the periphery as well as fovea center In bright light rods are overloaded we perceive primarily with the three sets of cones in the retina which have narrower spectral sensitivity roughly corresponding to red green and blue wavelengths Cones are concentrated mostly in the fovea so we have low spatial resolution in periphery Green cones most populous then red then blue hence our poor blue spatial sensitivity Perception of Light and Color 2 Some people are colorblind they have one or more sets of defective or poorly wired cones Other animals have fewer or more sets of cones 1 7 Facts from neurophysiology signals cones are combined in higher levels of processing in the retina and in the brain by neurons whose receptive fields point spread functions seem to come in several types spot detectors edge detectors and line detectors And each comes at a range of scales orientations and color



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