2. Red, green and blue (RGB): RGB is another way to use 3 numbers to specify a color instead of using an intensity-distribution curve or HSB
In addition to using Hue, Saturation and Brightness (HSB);
Many (but not all) colors can be described in terms of the relative intensities of a light mixture of a certain wavelength red, wavelength green and wavelength blue lights
650-nm red
530-nm green
460-nm blue
These are called the additive primaries
The mixing of the additive primaries is called additive mixing
Additive mixing is usually done by mixing primary color lights with different intensities but there are other ways to be discussed later
Demonstrate with Physics 2000
yellow
530-nm green
650-nm red
cyan
magenta
460-nm blue

3. Complementary additive colors
Definition of complementary color (for additive mixtures):
The complement of a color is a second color.
When the second color is additively mixed to the first, the result is white.
Blue & yellow are complementary B + Y = W.
Green & magenta are complementary G + M = W
Cyan and red are complementary C + R = W
Magenta is not a wavelength color— it is not in the rainbow
There is at most one wavelength complementary color for each wavelength color (Fig 9.9)
yellow
blue
magenta
green
cyan
red
white

4. Additive mixing of colored light primaries
Blue added to
green = cyan.
Green added to
red = yellow.
Red added to
blue = magenta.

5. Complementary colored lights (additive mixing)
Blue (primary)
and yellow.
Green (primary)
and magenta.
Red (primary)
and cyan.

6. What is partitive mixing?
Partitive mixing is another kind of additive color mixing but not achieved by superimposing colored lights!
Instead, it works by putting small patches of colors next to each other.
From a distance these colors mix just as though they were colored lights superimposed on each other
Examples:
Seurat pointillism
Color TV and computer screens (Physics 2000)
Photoshop example

7. Partitive mixing
Read the introduction and click on the “Light in Color” tab. Proceed to work the activity listed below.
Made from dots
Go through and write down at least 5 different color combinations from the program.

9. A colored filter subtracts colors by absorption.=
Cyan
filter subtracts
red
Yellow
filter subtracts
blue
Incident white light
Only green
gets
through

10. A colored filter subtracts certain colors by absorption and transmits the rest=
Magenta
filter subtracts
green
Cyan
filter subtracts
red
Incident white light
Only blue
gets
through

11. A colored filter subtracts colors by absorption.=
Magenta
filter subtracts
green
Yellow
filter subtracts
blue
Incident white light
Only red
gets
through

13. What is the effect of combining (sandwiching) different colored filters together?
Rules for combining the subtractive primaries, cyan, yellow and magenta:
White light passed through a cyan filter plus a magenta filter appears blue
White light passed through a yellow filter plus a magenta filter appears red
White light passed through a yellow filter plus a cyan filter appears green
Why?
cyan
yellow
magenta

14. Colored surfaces subtract certain colors by absorbing them, while reflecting others
White in
White in
Magenta out
Green out
Magenta surface
absorbs (subtracts)
green.
Green surface
absorbs (subtracts)
red and blue (magenta).

15. Green light on a magenta surface appears colorless because green is absorbed
Magenta light on a green surface appears colorless because magenta is absorbed
Magenta in
Green in
No color
No color
Magenta surface
absorbs (subtracts)
green.
Green surface
absorbs (subtracts)
red and blue (magenta).

16. Halftone Left: Halftone dots.
Right: How the human eye would see this sort of arrangement from a sufficient distance or when they are small.
Resolution: measured in lines per inch (lpi) or dots per inch (dpi); for example, Laser Printer (600dpi)

17. Color halftoning
Paper beneath
Printer's ink
Three examples of color halftoning with CMYK separations. From left to right: The cyan separation, the magenta separation, the yellow separation, the black separation, the combined halftone pattern and finally how the human eye would observe the combined halftone pattern from a sufficient distance.