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...Lecture notes on digital image processing prepared by dr prashanta kumar patra college of engineering and technology bhubaneswar unit i fundamentals transforms elements visual perception human systems the following figure shows anatomy eye in cross section there are two types receptors retina rods long slender cones generally shorter thicker structure not distributed evenly around operate differently more sensitive to light than at low levels illumination provide a response called scotopic vision respond higher their is photopic three basic these have different absorption characteristics as function wavelength with peak absorptions red green blue regions optical spectrum b g most fovea spread just about everywhere except relatively sensitivity lot overlap...