the physics of color - rey san andrew rimando
Post on 22-Oct-2014
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This PPT will help you gain additional knowlegde about the Physics of Color.TRANSCRIPT
THE PHYSICS OF COLORRey San Andrew Rimando
BSCivil Engineering
COLORSIs the VISUAL PERCEPTUAL PROPERTY
interacting in the eyes with the spectral sensitivities of the light receptors in different categories like RED, YELLOW, BLUE, GREEN, ORANGE, VIOLET.
Color categories and physical specifications of color are also associated with objects, materials, light sources, etc., based on their physical properties such as light absorption, reflection, or emission spectra.
Color derives from the Spectrum of Light (distribution of light powers versus wavelength)
Visible Light Spectrum; An Introduction
Normally when we use the term "light," we are referring to a type of electromagnetic wave that stimulates the retina of our eyes. In this sense, we are referring to visible light, a small spectrum from the enormous range of frequencies of electromagnetic radiation. This visible light region consists of a spectrum of wavelengths that range from approximately 700 nanometers (abbreviated nm) to approximately 400 nm. Expressed in more familiar units, the range of wavelengths extends from 7 x 10-7 meter to 4 x 10-7 meter. This narrow band of visible light is affectionately known as ROYGBIV.Each individual wavelength within the spectrum of visible light wavelengths is representative of a particular color. That is, when light of that particular wavelength strikes the retina of our eye, we perceive that specific color sensation.
Color Vision in the Eye
Three types of cones (color)One type of rod (B/W only)
Sir Isaac Newton - DISPERSION
Showed that light shining through a prism will be separated into its different wavelengths and will thus show the various colors that visible light is comprised of. The separation of visible light into its different colors is known as dispersion.
Each color is characteristic of a distinct wavelength; and different wavelengths of light waves will bend varying amounts upon passage through a prism. For these reasons, visible light is dispersed upon passage through a prism. Dispersion of visible light produces the colors red (R), orange (O), yellow (Y), green (G), blue (B), and violet (V). It is because of this that visible light is sometimes referred to as ROY G. BIV.
(Incidentally, the indigo is not actually observed in the spectrum but is traditionally added to the list so that there is a vowel in Roy's last name.)
The red wavelengths of light are the longer wavelengths and the violet wavelengths of light are the shorter wavelengths. Between red and violet, there is a continuous range or spectrum of wavelengths.
Wavelengths & Photons
Red Photon
Blue Photon
Green Photon
Yellow Photon
PrismSpectrum
Particles of light, called photons, each have a wavelength.
Additive Color Wheel
SpectralColors
There are No Photons
of These Colors
R
Y
B G
M
C
RedYellowGreenCyanBlueMagenta
Adding Color Lights
Stream ofred & green photons looks same as yellow photons(metamerism)
Theatrical lighting
or
YELL
OW
Eye toBrain
Notice overlap of red, green, & blue is seen as WHITE light
Newton’s Color Wheel
Prism spectrum is a straight line, so why did Isaac Newton describe color using a circular wheel?
Before we continue our discussion,
Let me show you some tricks in Color Wheel
The Color Wheel The color wheel is a
means of organizing the colors in the spectrum.
The color wheel consists of 12 sections, each containing one hue. A hue is a name of a
color on the color wheel.
This lesson will discuss each of the colors, color harmonies and how they are created.
The Primary Color Triad
The primary colors are, red, yellow and blue and are the purest and most intense of all the colors.
The intensity of a color is the brightness or dullness of a color. They form a triangle on the color wheel and are colors that cannot be mixed from any other colors. These are the only colors that can be found in nature.
red
yellow
blue
The Secondary Color Triad
The secondary colors are orange, green and violet and are duller than the primaries because they have been mixed together.
They form a triangle on the color wheel and are colors that are mixed from the primary colors.
Primary + Primary = secondary
orange green
violet
Red + yellow=orange
Blue + yellow= green
Red + blue= violet
The Intermediate (Tertiary) Colors These colors are yellow-
orange, yellow-green, blue-green, blue-violet, red-orange, red-violet and are even duller than the secondary colors because the primary has been mixed with a secondary.
These 6 colors are formed by mixing a primary and a secondary color.
Primary + Secondary = Tertiary
yellow + orange=yellow-orange
yellow + green = yellow-greenblue + green =blue-greenblue + violet = blue-violet
red + violet =red-violetred + orange = red-orange
Yellow orange
Red orange
Red violet
Blue violet
Blue green
Yellow green
COLOR
WHEEL
Hue-Saturation Diagram
Eye is not a perfectoptical instrument.
Color “wheel” isactually distortedcone shape.
Rim is full saturation,center is white
What color is present in the center?
ANS= WHITE
Hue, Saturation, Value
Color wheel is nota single wheel butstack of wheels that range invalue.
The Warm and Cool Color Scheme
Warm colors range from: yellow yellow-orange orange red-orange red red-violet
Cool colors range from:
yellow-green green blue-green blue
blue violet violet
Grayscale
A value scale is a scale of grays running from black to white.
Spectral Reflectance Curves
When white light shines on a colored object, some photonsabsorbed, others reflected by the object’s surface.
White Re
d
Neutral Colors
Neutral Colors are those colors not found on the color wheel but are mixed by other colors on the color wheel.
White Brown Gray
Black
Basic Color Schemes
MONOCHROMATIC
Having only one color. Here I used all shades of red to create the design
Basic Color Schemes
ANALOGOUS
Uses Colors that are next one another on the Color Wheel
Basic Color SchemesCOMPLEMENTARY
Consists of colors that are opposite of one another on the color wheel.
Basic Color Schemes
TRIAD
Consists of a color and the colors to the left and right of its complement
Let’s do an example..
Let’s Try!
Negative After-image
Stare, unfocused, at the red cross for 10 seconds then look at white wall
Negative After-image
Cyan
Negative After-image
Stare, unfocused, at the flag for 10 seconds then look at white wall
Negative After-image
Cyan Magenta Yellow
Simultaneous Contrast
Are the two gray bars the same shade of gray?
Yes, the presence of a nearby color affects perception of both hue and value, shifting both towards complement
Does the gray bar look slightly bluish?