then flattens out and goes no higher (fig. 4-11). This
condition makes it difficult to photograph the ground.
In these circumstances, you can use film with extended
red sensitivity or a red filter to help cut through the haze.
There is nothing you can use to cut through the smoke.
Thermal shimmer is another condition with which
you should be concerned. Thermal shimmer is the
result of heated air moving upward. When thermal
shimmer is occurring, distant objects appear to shimmer
because the light rays are being refracted by the rising
heated air. This occurrence can obscure minute detail
in high-altitude photography. When thermal shimmer
exists, you should take enough photographs to ensure
that subject detail occurs in at least one photograph.
Good weather conditions for aerial photography are
generally considered to be clear with 5 to 10 knots of
wind (to help blow off smoke and smog) and visibility
of 7 miles or more. Minimum conditions are generally
considered to be scattered clouds with visibility of 6
miles. When weather conditions are poor, shoot
low-oblique photographs from relatively low altitudes.
This helps to minimize the effects of smoke and haze.
After you have gained some experience in taking
hand-held aerial pictures, you will probably have a
preference for a particular type or model of aircraft.
Hand-held aerial photographs can be made from almost
any aircraft. However, there are some generally
accepted preferences, such as high-wing aircraft or
relatively slow-flying aircraft. Most slow-flying
aircraft have a window, door, or hatch that can be
removed or opened to simplify unobstructed
photography. A high-wing plane is preferable to a
low-wing plane because the wing is out of the field of
view of the camera.
Helicopters provide photographers more freedom
to work at lower altitudes, but there are certain
misconceptions about them (fig. 4-12). One of these
misconceptions is that the platform can be suspended
Figure 4-12.Helicopter used in an aerial photographic assignment.