LECTURE 2

Color Engineering

Intensity, Hue, and Saturation

Brightness, Colorfulness, and Hue

Related and Unrelated Color

Unrelated color Color perceived to belong to an area or object seen in

isolation from other colorsRelated color

Color perceived to belong to an area or object seen in relation to other colors

Brightness

Attribute of a visual sensation according to which an area appears to emit more or less light

Absolute level of the perception

Bright

Dark

Bright? White

Lightness

The brightness of an area judged relative to the brightness of a similarly illuminated area that appears to be white or highly transmitting

Related brightness (normalized)

Sample - Brightness

Colorfulness

Attribute of a visual sensation according to which the perceived color of an area appears to be more or less chromatic

Chroma

Colorfulness of an area judged as a proportion of the brightness of a similarly illuminated area that appears white or highly transmitting

Relative colorfulness As lightness can be thought of as relative

brightness

Saturation

Colorfulness of an area judged in proportion to its brightness

Colorfulness of a stimulus relative to its own brightness

Chroma Colorfulness relative to white

Colorful

Dull

Colorful?

Sample - Colorfulness

Hue

The degree to which a stimulus can be described as similar to or different from stimuli that are described as red, green, and yellow

Sample - Hue

Gray and Brown

Gray Achromatic color with low lightness

Brown Orange with low lightness

Change backgroundUnrelated colors

Hue, brightness, colorfulness, saturationRelated colors

Hue, brightness, colorfulness, saturation, lightness, chroma

Definitions in Equations

Chroma: colorfulness relative to the brightness of a similarly illuminated white

Saturation: colorfulness of a stimulus relative to its own brightness

Lightness: ratio of the brightness of a stimulus to the brightness of a similarly illuminated white stimulus

Definitions in Equations

Saturation: ratio of colorfulness to brightness

Specify Color Appearance

Brightness, lightness, colorfulness, chroma, and hue

Saturation is redundantNeed 5 out of 6 to specify color appearance

Brightness-colorfulness vs. lightness-chroma

Brightness-colorfulness matching vs. lightness-chroma matching

Example - photo Yellow school bus outside

Colorfulness high, chroma high, brightness high, lightness high

Photo of yellow school bus inside Colorfulness low, chroma high, brightness low,

lightness high Photo of yellow school bus outside

Colorfulness high, chroma high, brightness high, lightness high

Key: reflected energy

Reproduction at Higher Luminance

Reproduction at Lower Luminance

Brightness-colorfulness vs. lightness-chroma

Example - projector Overhead projector 35mm slide projector

Summary

Related and unrelated colorBrightness and lightnessColorfulness and chromaSaturationHue5 of 6 variablesBrightness-colorfulness vs. lightness-

chroma