Light and the Eye

• In a healthy eye, light enters and is focused on the retina.

• The retina is made of two types of cells, cones and rods, they both absorb light.

• Absorption of light causes chemical reactions to convert light energy into nerve impulses that are sent to the brain.

• Cones allow you to see colors.• Rod are sensitive to dim light and useful for night

vision.

Light and Color

• Whitehite light is made up of all the wavelengths of visible light.

• Red• Orange• Yellow• Green • Blue• Indigo• Violet

Primary Colors of Light• The simplified spectrum is the primary colors:

– Red, Green, and Blue

• Addition of these colors creates all the colors.• TV’s and computer monitors use RGB• Tiny pixels on your screen are generated using

only these three primary colors of light.

Color Addition•Color addition only works with pure light.

•Addition of primary colors creates complementary colors:

Red + Green = Yellow

Blue + Green = Cyan

Red + Blue = Magenta

Complementary Colors

• Two colors of light that add together to produce white are complementary colors.

• For example: Red + Green = Yellow

• Red + Green + Blue = White

• Yellow + Blue = White

• Blue and Yellow are complementary colors of one another.

Color Subtraction• Color subtraction

occurs with paint, crayons, dyes, and filters.

• These absorb some colors and reflect the colors your eyes see.

Color Subtraction

White light (made up of red, green, and blue) strikes a surface. The red dyes absorb (or subtract out) the green and blue light and reflect the red dye back to your eyes. That is why a red object appears red in white light.

Color Subtraction

Color Printers

• Use the complementary colors, Magenta, Yellow, and Cyan

• You can produce a large range of reflected colors by adjusting the strengths of each secondary color.

• The smaller the dots, the sharper the image.

How Stuff Works – Color Negatives & Printing

Color Television