are most useful for increasing general outdoor color saturation and contrast.
Polarizers can darken a blue sky, a key application, on color as well
as on black-and-white film, but there are several factors to remember when
doing this. To deepen a blue sky,
it must be blue to start with, not white or hazy.
Polarization is also angle-dependent.
A blue sky will not be equally affected in all directions.
The areas of deepest blue are determined by the following "rule of
thumb." When setting up an
exterior shot, make a right angle between thumb and forefinger.
Point your forefinger at the sun.
The area of deepest blue will be the band outlined by your thumb as it
rotates around the pointing axis of your forefinger, directing the thumb from
horizon to horizon. Generally, as
you aim your camera either more into or away from the sun, the effect will
gradually diminish. There is no
effect directly at or away from the sun.
Do not pan with a polarizer, without checking to see that the change in
camera angle doesn't create undesirable noticeable changes in color or
saturation. Also, with an
extra-wide-angle view, the area of deepest blue may appear as a distinctly
darker band in the sky. Both
situations are best avoided. In
all cases, the effect of the polarizer will be visible when viewing through
need approximately 1-1/2 to 2 stops exposure compensation, usually without
regard to rotational orientation or subject matter.
They are also available in combination with certain standard conversion
filters, such as the 85BPOL. In
this case, add the polarizer's compensation to that of the second filter.
camera optical systems employ internal surfaces that themselves polarize
light. Using a standard (linear)
polarizer will cause the light to be further absorbed by the internal optics,
depending on the relative orientation. A
Circular Polarizer is a linear one
to which has been added,on the side facing the camera,
a quarter wave "retarder." This
"corkscrews" the plane of polarization, effectively depolarizing it,
eliminating the problem. The
Circular Polarizer otherwise functions in the same manner.
Combine the Tiffen ENHANCING filter with a Polarizer filter for more dramatic