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?