CHM ART Activity 3 Additive and Subtractive Mixing

When white light enters a material the color perceived is the result of the material absorbing all visible λ except for the apparent color which is reflected.. Subtractive Color Mixing S

Activity 3: Color Mixing Why?

 Ever since kindergarten we are taught that red paint and blue paint swirled together makes purple but it’s never really explained why this color transformation occurs So how do colors mix? It may appear that colors meld together magically to form a new hue but in reality the observed result is due to mixing in either subtractive or additive

processes

Learning Objectives

 Understand the concepts of Additive and Subtractive Mixing

 Be able to discern the resultant color when various pure and impure color lights or pigments are mixed

New Concepts

 Color mixing

Vocabulary

 Subtractive mixing

 Additive mixing

 Pure and impure pigments

 Subtractive Primary colors

 Additive Primary colors

 Cyan

 Magenta

Visible Light Review

When white light passes through a glass prism the visible spectrum emerges in the rainbow we name as red –

orange – yellow – green – blue – indigo – violet These colors are actually the various wavelengths (λ) of pure light from 400nm to 700nm that make

up the visible spectrum

http://www.greatreality.com/ColorComp.htm

When white light enters a material the color perceived is the result of the material absorbing all visible λ except for the apparent color which is

reflected For example, when light strikes a piece of red paper, the chemical constituents of the paper absorb the shorter λ corresponding to green and blue and transmit or release the longer λ, those corresponding to red For each pure spectral color, a reflectance curve indicates when light is released

or bounced off of a material

www.sabic-ip.com

Why is fluorescent light often considered to have a

“cool” hue?

www.candle-web.co.uk

So, what occurs when the illuminated material (as is the

case for most paints, inks and dyes) is not spectrally

pure? How is the viewed color being generated? It is

often assumed that pigment colors are adding together

to make a new hue when actually the reverse,

subtraction, is the case

Subtractive Color Mixing

Subtractive Mixing is a method of generating color

occurs when white light enters a solid medium Depending on the chemical nature of the material, certain λ of light will be absorbed (ie “subtracted” or removed from consideration) The remaining λ are refracted (bent) and reflected yielding the color perceived The components in a colored material are not usually “pure” meaning that they absorb all but one λ of light

If a paint is made of blue and yellow pigments, what colors are

absorbed? What colors are reflected?

Primary pigments are those three colors that when combined produce black

(ie all light is absorbed) The primary pigments in Subtractive Mixing

are as follows:

Yellow

Cyan – “blue-green”

Magenta – “red-blue”

www.horrorseek.com

Complete the column in the table below with the correct color of light for the

λ Absorbed

Primary

Subtractive Color λ Reflected λ Absorbed Apparent Color

Magenta Red, Blue

Activity

Using provided white paper discs and colored paint provided, paint one disc blue and one disc yellow Set these aside In a palette with indentations, mix some of the blue and yellow together Take one additional white disc and paint it with the result of the mixing Explain the results of painting all three

of the discs in the table below:

Disc

number Color Observed Explanation (colors absorbed)

1

2

Additive Color Mixing

The making of color with light as the medium follows a different pathway

called Additive Color Mixing When examining the process of coloration

by an additive method, the medium involved is wavelengths (λ) of

transmitted light superimposed on one another such that the colors combine

or “add” together to make a new λ or new color

Primary pigments are those three colors that when

combined produce white light The primary pigments in

Additive Mixing are as follows:

Red

Blue

Green

www.horrorseek.com

A demonstration of Additive Mixing would occur if beams of colored light were shined upon a white wall If the beams were shined adjacent to one another their separate colors would be seen If the beams are subsequently superimposed, the original colors would “add” and a new color would appear

Activity

Gather 3 students/group and using flashlights with colored gel covers (red, green & blue), follow the procedure below

1 The first student projects the red light onto a white wall

2 The second student separately projects blue light and then the third student projects green

3 Lastly, have each student overlap their light source with ⅓rd of the others

What color is at the center? Why?

For each primary color a complementary color exists which when combined

with the primary results in grey, black or white The complementary color results for Additive & Subtractive Mixing are shown below:

Colors Yielded

Additive Mixing (ie lights) Subtractive Mixing (ie pigments)

Red - Cyan white black/grey

Blue - Yellow white black/grey

Green - Magenta white black/grey

http://www.greatreality.com/ColorComp.htm

For generating Subtractive Colors through the use of pigments or inks, any color can be produced by mixing correctly proportioned amounts of cyan, yellow and magenta EXCEPT for a true black In this case a true black

pigment must be added as the mixing of cyan, yellow and magenta often yields a muddled black

The CMYK color printing model utilizes cyan,

magenta, yellow and black inks instead of mixing

the first three to remove all light hence make black This method is called 4-color printing and is more appealing visually by producing a true black

The following illustration demonstrates the production of color by both the Additive and Subtractive Mixing methods

www.quickstep.com

Activity

Using the supplied paints and colored filters on flashlights, demonstrate each

of the following examples and complete the table below:

Subtractive?

Red paint + Blue paint

Green light + Blue light

Red light + Blue light

Magenta paint + Yellow

paint

Magenta + Cyan + Yellow

paints

Red + Blue + Green lights

DONE!