20 color space

7/31/2019 20 Color Space

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Three attributes which are described byvarious labels

Hue▪ color

Saturation

▪

chroma, intensity

Value

▪ brightness, lightness, luminosity, brilliance



Typically, the first thing we usually notice about a

color is its hue

Hue is one of the

universal variablespresent in all colors



Describes the shade of color and where that color isfound in the color spectrum

The range of hues, H, issymbolized as a circlerepresented by valuesfrom 0 to 360

The dominantwavelength of a colorindicates its hue



Places a particular color into its family or class

Such classes of color are red, yellow, green,

blue, and violet When we look at a red light, we experience the

sensation of a red hue

With the word "red" we are conveying to othersthe idea of a particular hue



Chromatic colors

Perceived colors that posses a hue

Achromatic colors

Perceived colors that do not posse a hue

▪

Black▪ White

▪ Grey



Colorfulness in proportion to its brightness

It is the dimension in which color can be

more or less vivid

Saturation concerns the proportion(concentration) of achromatic component

perceived in a color

Saturation may vary from zero to 100%



Indicates its hue color

Hue is that which distinguishesone color from another

more dominate the wavelengththe greater is the purity orsaturation of the color



Runs from neutral gray through pastel tosaturated colors

A vivid color usually has a high saturationlevel - not much gray

As the saturation decreases

▪ amount of gray increases

▪ color becomes less vivid



By placing a gray at one endof a linear series

and a fully saturated hue of the same value at the other

we can make a scale in which

hue is constant whilesaturation varies



Distinction between any color and a lighteror darker one

Relative description of how much light is

coming from the color

If the color reflects a lot of light, wewould say that it is bright; value is related

to the brightness White values have the maximum

brightness, black values have no

brightness



Can become darker or lighter on a slidingscale

All colors have potentially the same andpotentially different value

▪ This extreme adaptation makes value

contrast different than hue contrast

▪ While red cannot be yellow it can be thevalue of yellow



The amount of stimulus change required todetect a difference

difference threshold the smallest change in stimulation that a

person can detect

the difference between two stimuli that isdetected as often as it is undetected



In a printed band of continuously blendedgrays from black to white

a person of extreme visual acuity can perceive asmany as 150 changes

and in nature where the contrast range is

considerably greater, this number is in thethousands



Black and White of equal amounts, whethercomposed of pigment mixtures or light

Does not produce a gray which appears to splitthe difference between them

The gray which does reflects only eighteen

percent of white light



Most scenes and subjects reflect an overallaverage of about 18% of the light that strikes

them



From the middle values to the dark values

The amount of light required to produce a

just-perceivable difference is relativelysmall



This range can be thought of as the amountof light illuminating a color

For example

when the hue is red and the value is high the colorlooks bright

When the value is low it looks dark



The human eye candistinguish about

128 different hues 130 different

saturation levels

So we can distinguishabout 380,000 colors



The hue is given by the angleabout the vertical axis red at 0° yellow at 60° green at 120° cyan at 180° blue at 240° magenta at 300°

Note that the complementarycolors are 180° apart



Simply put, color spaces define boundarieswithin the visible color spectrum

Perimeter Fence all colors inside the fence may be represented in

that color space; all colors outside are not

The area inside the fence is referred to as the

color space's color gamut



Represented byvarious solid

shapes Cubes

Cones

Polyhedra



Gray Spaces RGB-Based Color Spaces

CMY-Based Color Spaces Device-Independent Color Spaces



Single component Ranging from black to white. Gray spaces are

used for black-and-white and grayscaledisplay and printing



Three-dimensional

red, green and blue intensities

Device-Dependent

colors produced by RGB specifications vary from device todevice

RGB space examples sRGB

Adobe 1998



Used in color printing systems They are device dependent and subtractive in

nature The groups of color spaces within the CMY

family include

CMY

CMYK



Photographic Color Film

Positive and negative

Photographic color print paper



Models the way inks or dyes are applied topaper in printing

The name CMYK refers Cyan

Magenta

Yellow

Black



Primaries

Cyan, magenta, yellow

Secondaries Red, green, blue

Theoretically black is not needed

But when full-saturation cyan, magenta, and

yellow inks are mixed equally on paper result is

usually a dark brown, rather than black



subset of colors which can be accuratelyrepresented in a given circumstance

within a given color space or by a certain outputdevice

complete set of colors found within an imageat a given time



Used mainly for color models Translating between RGB & CMYK models

Meant to be true representations of colors asperceived by the human eye



1. Spectrally opponent processes

red vs. green yellow vs. blue

2. Spectrally non-opponent processes

black vs. white



cross-platform standard

provide color management systeminformation

to convert color data between

device dependent color spaces



Contain the color characteristics for eachdevice

obtain their openness by using a well-definedreference color space



To provide the closest possible color matchbetween devices given their inherent

differences Each device looks and works differently,

and may produce different results



Profiles saved within graphics documents andimages

allow movement of color data betweendifferent computers, networks and operatingsystems

without having to worry if thenecessary profiles are present on thedestination systems



Compresses the total gamut from onedevice's color space into the gamut of another device's color space



range of all possible colors which can berepresented or produced on a device



Reproduces the original image colorsaturation when converting into the target

device's color space the relative saturation of colors is maintained

from gamut to gamut primarily designed for business graphics

the exact relationship between colors is not as

important as are bright saturated colors



When a color in the current color space is outof gamut in the target color space

mapped to closest possible color within thegamut of target color space



Colors match exactly with no adjustmentmade for white point or black point that

would alter image's brightness Absolute colorimetric is valuable for

rendering “signature colors”

colors highly identified with a commercial

product

▪ yellow used by Eastman Kodak

▪ red used by Coca-Cola

20 color space

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