by
John Pickle,
Museum of Science, Boston
A
great deal of time is spent working with young students in
making colors with paints, yet there is another world of color
youth and adults need to explore: the colors made by mixing
light. Ask most people what happens when they mixed all of
their paints in their paint set together, and there is a universal
agreement that a dark color will appear. And most people recognize
that white sunlight passing through a prism creates a rainbow
of color, but few of us ever think of this discrepancy: mixing
many colors in paint make a dark color and mixing many colors
in light makes white.
Colors
made by mixing light are the foundation of color computer
and television screens, and are a key component in today’s
information technology. Yet we don’t often have the
opportunity to play and experience how millions of colors
are made by mixing varying amounts of red, green, and blue
light. Several activities were developed in the "Interpreting
Satellite Images" learning materials to allow people
to explore the colors made by adding light.
The
first computer program, TriColor, lets people make over a
million colors by changing the intensity of red, green, and
blue light on the computer screen. Intensities are based on
percent, with 0% meaning no contribution and 100% representing
maximum intensity. One of the first observations are that
the intensities of red, green, and blue do not add up to 100%.
For example, black is made with 0% red, 0% green, and 0% blue,
and white is made with 100% of red, green, and blue. You might
want to think of the three intensities as coordinates of the
final color in a color cube with axes of red, green, and blue.
For a good visual model, see http://www.colorcube.com.
The
goal of exploring colors made by light is for people to be
able to identify the intensity components in red, green, and
blue because this skill is critical when interpreting satellite
images. Intensity measurements of invisible wavelengths of
light are displayed as red, green, or blue, and the colors
of the resulting image represent the surface and/or atmospheric
characteristics. In order to practice identifying the intensity
components of colors, Game_TriColor allows people to play
the computer or a classmate in identifying either randomly
generated colors or those created in secret. Hints are provided
after each guess to provide guidance.
There
are two key skills required in identifying the colors with
red, green, and blue:
(1) matching the lightness of the color (the greater the intensities, the lighter
the color and conversely, the darker the intensities, the darker the color)
and
(2) the mathing the relative contribution of red, green, and blue. For example,
pink is a very light color, so there are large amounts of red, green, and blue
but the dominant color is red. Therefore, a nice pink can be made with 100%
red, 80% green, and 80% blue. To help students measure their skills, Report_Tricolor
keeps track of the guesses made for ten randomly generated colors, and a report
is generated at how well they identified the overall intensities and how well
they identified the dominant and least dominant color. The report appears on
the computer screen, is saved to a file with the student’s identification,
and may be printed as an assessment.
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