Human Eye Some interesting facts Useful fact Rod cells: Cone cells:

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Presentation transcript:

Human Eye Some interesting facts Useful fact Rod cells: Cone cells: Image credit: Wikipedia (Fovea) Human Eye Some interesting facts Rod cells: requires only low light b/w vision blur, all over retina EXCEPT fovea Cone cells: requires bright light, Color vision: three kinds of cone sensitive to roughly RGB wave lengths acute, sharp image, located at the fovea Dynamic range and adaptation Useful fact Lens is like a low pass filter!! Image credit: Wikipedia: fovea

Color? Colorimetry Remember our eye? Color representation: Measurement description of color Remember our eye? 3 types of Cone cells: S M L Each responsive to different visible wavelength! Color representation: based on three components! Color perception is SUBJECTIVE! CIE Standardization effort (self reading) Image credit: Wikipedia: cone cells

RGB: Additive Color (R, G, B): 0 – off, 1 – full on Components are added E.g., Our eyes, CRT, LCD, Projector RGB – most often used range between 0 to 1 RGB: a Color Cube Image credit: Wikipedia: Additive Color B (1,0,0) G (0,1,0) R (1,0,0)

Additive Color Easier for human to HSV Hue, Saturation, Value separate color from “intensity” HSV Hue, Saturation, Value HSL (Luminosity, Lightness) HSB (Blackness?) Demo: http://demos.telerik.com/aspnet-ajax/colorpicker/examples/default/defaultcs.aspx RGB to HSV Demo: http://www.flashandmath.com/advanced/color/RGBtoHSV.html

Additive Color: Example Microsoft Office Color Picker Hue: Which color. Range: 0 to 360, degrees around the cone circumference (MS normalized this to 0 to 255) Luminosity: the “intensity” or brightness. Range: 0 to 100, height of the cone (MS normalized this to 0 to 255) Saturation: how colorful. Range: 0 to 100, distance from the center of the cone (MS normalized this to 0 to 255)

Subtractive Color The expensive printer cartridges CMY – filtering white color Each acts as a filter of (1,1,1) E.g., White Paper: (1,1,1) Through Y filter => (1,1,0) Through M filter =>(1,0,0) Through C filter => (0,0,0) The filter (ink pigment) leaks Black is not very black That’s why the separate black cartridge Yellow (1, 1, 0) Image credit: Wikipedia: Subtractive Color Cyan (0, 1, 1) Magenta (1, 0, 1)