Human Visual PerceptionColor TheoryAdditive and Subtractive ColorColor BlindnessColor Theory• White light is a perception of the human mind• White light is composed of all the wavelengths of visible light or equal combinations of RGB• Our eyes have Red, Green and Blue sensitive cells (cones) and light intensity cells that are insensitive to color (rods).• Mixing Red, Green and Blue light (not true with pigments)will be perceived as white light• That’s how an RGB monitor works++ = =Color CubeHue (color’s name)Saturation (Chroma)More SaturatedLess SaturatedRed Yellow Green Cyan Blue MagentaLuminance (Brightness) RangeLuminance (Brightness / Value)Brighter(GreaterLuminance)Darker(Lower Luminance)Color RGB• RGB (Red, Green, Blue)• Range 0-255 (0,0,0) tuple– 24 bit color – 8 bits per color - 3 bytes – 1 byte per color– Red(255,0,0) Green(0,255,0) Blue(0,0,255)– Cyan(0,255,255) Magenta(255,0,255) Yellow(255,255,0)– White(255,255,255) Black(0,0,0) Gray (128,128,128)– Supports 2^24 = 256^3 = 16777216 (16 x 10^9 individual colors)– 48 bit color (16 bits each RGB) 2^48 = 281 x 10^12 colors (more variations than the human eye can distinguish)• Color complements (adding one - subtracts the other from the overall color balance)–Red and Cyan– Green and Magenta– Blue and Yellow– White and BlackColor RGB• RGB Red Green Blue• Range 0-255 (0,0,0) tuple– 24 bit color – 3 bytes – 1 per color– Red(255,0,0) Green(0,255,0) Blue(0,0,255)– Cyan(0,0,255) Magenta(255,0,255) Yellow(255,255,0)– White(255,255,255) Black(0,0,0) Gray (128,128,128)– Supports 2^24 = 256^3 = 16777216 (16 x 10^9 individual colors)– 48 bit color (16 bits each RGB) 2^48 = 281 x 10^12 colors (more variations than the human eye can distinguish)• Color complements (adding one - subtracts the other from the overall color balance)– Red and Cyan– Green and Magenta– Blue and Yellow– White and Black(Additive) Color Wheel• See http://www.themodelmakersresource.co.uk/facts/facts011.htmlThe Color Wheel (Cube)shows various saturations of colorsColor HSV / HSL • HSV - Hue Saturation Value• HSL - Hue Saturation Lightness• Hue - Relative Color on the color wheel(0 ° - 360°)• Saturation (Chroma) - the amount of color intensity v. gray – 0-100%• Value (Luminance)/Lightness – the amount of white/black added to the color.H = 127Sat = 255 Sat = 64Sat = 128 Sat = 0H = 85 H = 180 H = 43V = 64V = 128 V = 32 V = 216Color “salami” in HSVValue (Lightness)Hue around the circle, Saturation distance from the centerSaturationHue• <<Freehand Color Picker Demo>>Color Demo• <<pop up the color chooser for the square below. Vary the values in RGB, HSV spaces.>>•Same “color” in different color modelsH: 139S: 197V: 0R:0G:0B:0• Questions• Comments•0.5(Subtractive) Color CMYK• CMYK - Cyan Magenta Yellow blacK• C+M+Y inks produces a muddy brown NOT black, so they added the black, too.• Used in the printing industry (Pigments)• Subtractive Primary Colors – can mix any other color from them++ ===+For Paints, Pigments, Dyes and Filtering Light• They are subtractive (they absorb light)• Pigments are imperfect absorbers and impure – that makes color mixing paints, dyes or filtering light more art than science.• Often say ROYGBIV not RYGCBM• <notice that artists think RYB not RGB are the primary pigments – you can mix any color from them – not quite true/>• Hue the names of colors (for pigments)(primary) red, yellow, blue(secondary) orange, green, violet(tertiary) red-orange, orange-yellow, yellow-green, green-blue, blue-violet, red-violettint = add whiteshade = add blackSubtractive Colors(filters absorb colors)• http://home.att.net/~B-P.TRUSCIO/COLOR.htm• Light is additive• Pigments are subtractive• Add R G B lights together you get WHITE• Add R G B pigments together you get BLACK– (well more like a muddy brown)• You see what colors are reflected from an object – the object absorbs the colors you don’t see– it absorbs the complimentary colors of te one you see.Light vs. Pigments(Illumination vs. Reflectance)• The red apple reflects red light (and absorbs all others - green and blue).• The green apple reflects green light (and absorbs all others red and blue)• Is the color you see really the color of an object or is it just the opposite?Mixing 3 specific wavelengths vs. continuous wavelength - the eyes see the same color==I see white==I see magentaMixing 2 specific wavelengths vs. single wavelength - the eyes see the same colorMixing 2 specific wavelengths vs. single wavelength - the eyes see the same color==I see cyanAdditive Color Combinations(shining lights together)Contrast• “difference” between the foreground and background colors or if shades of gray, difference in luminanceGray Text on White Background has lower contrastWhite Text on Black Background has high contrastBlack Text on White Background has high contrastYellow Text on White Background has lower contrastYellow Text on Black Background has higher contrastYellow Text on Green Background has lower contrastYellow Text on Blue Background has higher contrastContrast• A color on its complement usually has a very high contrast – sometimes too much – often caused by your hardware! Ex: color fringing and “ringing” on TV• Usually looks a little “circus like”• Black text on a white background is usually a good place to start for readabilityBlue Text on Yellow BackgroundGreen Text on Magenta BackgroundMagenta Text on Green BackgroundYellow Text on Blue BackgroundCyan Text on Red BackgroundRed Text on Cyan Background• Questions• Comments•1.0Tools to demo color theory• Click to see demos• Hue and saturation http://psych.hanover.edu/JavaTest/Media/Chapter6/MedFig.ColorDimensions.html• Additive Color Mixing http://psych.hanover.edu/JavaTest/Media/Chapter6/MedFig.ColorMixer.html• Color matching experiments http://psych.hanover.edu/JavaTest/Media/Chapter6/MedFig.ColorMixer.htmltry yourself!• Cone Response to Light demo http://psych.hanover.edu/JavaTest/Media/Chapter6/MedFig.TrichromatCones.html• See paper http://psych.hanover.edu/classes/sensation/chapters/Chapter%206.docCross section of Human EyeFrom http://www.inventoland.net/imaging/uc/understandColor.pdfHuman eye sensitivities (MBCGYR)From