reflected in more than one direction.
This form of reflected light is
termed diffused.
Practically all surface media reflect both specular and
diffused light; smooth surfaces reflect more specular light, and rough
surfaces reflect more diffused light. Since diffused light is more common
than specular light, it is this light that is of greatest value in
photography.
Keep in mind that all surfaces vary in their ability to
reflect light.
c. Selective Reflection.
Selective reflection is a characteristic
displayed by certain metals. Gold, copper, and brass are some of the metals
that exhibit these qualities. Specular reflections from many metals tend to
be white, assuming a white light source.
Gold, for example, selectively
reflects red and yellow light, giving it its characteristic color.
A
selective is a reflection that is not white but the same color as the
object.
d. Haze.
Variations in atmospheric density caused by airborne
particles such as dust, droplets of water, and ice crystals effect the
shorter wavelengths in the spectrum to a greater degree. When light enters
the atmosphere, the shorter wavelengths of light are scattered more than
longer wavelengths. This alters the quality of the incident light. Haze is
the result of light scattered by the atmosphere.
e. Scattering.
The redness of the sun at early morning and late
afternoon is caused by atmospheric scattering of light.
At this time of
day, the amount of atmosphere that light waves must penetrate is increased
due to the angle of the sun.
Increased atmospheric density results in increased scattering of the blue
wavelengths. The higher penetration ability of red light waves produces our
colorful sunrises and sunsets.
f. Interference. Have you ever noticed the patterns of color produced
by oil on the surface of water and wondered what caused them?
They are
produced by light wave interference from two surfaces spaced a few
nanometers apart.
When light is reflected from these two surfaces, a
portion of the reflected light will be cancelled when the two light waves,
one reflected from each surface, meet. This interference produces the color
you see.
The color patterns formed are known as Newton's rings.
Under
certain circumstances, Newton's rings can present problems when working with
color materials. They may occur if you are printing color material using a
glass negative carrier.
The irregular contact between the glass and the
negative surface may produce interference effects.
This effect may also
occur in glass-mounted slides. The use of a glassless carrier and a special
glass for the slide mounts can remedy these problems.
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