LESSON 2
PHOTOGRAPHIC FILTERS
TASK
Describe the theory of photographic filters, their general construction, and
their proper use in black-and-white photography.
CONDITIONS
Given information and diagrams pertaining
to
the
theory,
construction,
selection, and use of photographic filters.
STANDARD
Demonstrate competency of the task skills and knowledge by correctly
responding to a minimum of 80 percent of the multiple-choice test covering
the theory of photographic filters, their general construction, and their
proper use in black-and-white photography.
REFERENCES
TM 11-401-1
Learning Event 1:
DESCRIBE THE COLOR OF LIGHT
1.
In Lesson 1, you learned about exposure. You focused carefully, held
the camera steady, squeezed the shutter release, and took a perfect picture.
So why isn't the print as great as the picture you saw in your mind's eye?
The red apple in the green tree stood out clearly, but in the black and
white picture, it looks almost the same shade of gray as the leaves. And
that blue blouse and yellow dress the girl was wearing, both look gray; it's
hard to tell which is which. And what happened to the landscape with those
beautiful white clouds so sharp against a brilliant blue sky - the clouds
are barely visible and the sky is a washed-out gray. What went wrong? More
important, what can be done about it? By using appropriate filters with the
right film emulsions, you can make corrections for the film's tendency to
misrecord the scene you wanted.
2.
Wavelengths of light.
To understand filters, you must first
understand a few basic things about light.
Perhaps you learned in school
that white light is made up of the colors of the rainbow - red, orange,
yellow, green, blue, indigo, and violet (fig 2-1).
You might have also
learned that light travels in waves, somewhat like the expanding ripples
created when you toss a rock into a quiet pool of water. One big difference
between the two (among many) is the distance between crests of the waves.
The distance between crests is called a wavelength. In water, the distance
might be a foot or so. With light, however, the distance between crests of
the waves is measured in billionths of a meter, called nanometers for short,
and abbreviated still further
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