see a single wavelength, it must be isolated and presented alone.
For
example, the eye cannot be selectively turned to red, green, or
blue
radiations when presented in combination.
(a) However, it is possible for the eye to visualize colors not
present in the spectrum.
If equal amounts of red and blue wavelengths
strike the eye, we see a purplish or magenta color.
(b) Because red and blue are at opposite ends, magenta does not
exist in the visible spectrum.
We see magenta because the surface is
reflecting equal amounts of red and blue radiation and absorbing the green.
(c) Yellow is another example of this phenomenon. Yellow occupies
only a small part of the visible spectrum, approximately 575 to 590
nanometers.
If only yellow radiations are reflected to the eye, the
reflecting surface appears black.
Most yellows seen by the eye are the
result of the surface absorbing blue radiations and reflecting the red and
green.
(3) Color vision takes place when the receptors in the eye receive
various combinations of visible wavelengths and transmit them to the brain.
Therefore, color vision is both a physiological and a psychological
(a) Any damage to the collection, transmission, or reproduction
system will affect color vision. Damage to the optic nerves, for instance,
can result in color blindness.
(b) There are, conceivably, as many variations in the development
of eyesight as there are in fingerprints.
(c) Color vision depends upon the individual; therefore, it is
subjective.
4.
Producing Color.
When you think about primary colors, those colors that cannot be made but
are used to make all others, you are likely to recall the colors red,
yellow, and blue.
These are the colors that we learned about in grammar
school. These are primaries for pigments, such as paint. When we speak of
light, it's a different story.
a. Producing Color with Light. It is possible to produce any color by
combining amounts of red, green, and blue light.
To control the various
components so that we can achieve a specific result, it is necessary to use
filters.
There are many different types of filters, each having definite
applications in the photographic process.
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