CAMERA FILTERS © Ira Tiffen 11
The number of directions that lines run in determines the number of points produced.
Lines in one direction produce a two-pointed star, just a streak through the center of the
light. There are 4, 6, 8, 12 and more points available. With an 8 or 12 point filter, the many
star lines will tend to overpower the rest of the image, so use them carefully. Although the
more common types have a symmetrical arrangement of points, they can also be obtained
with asymmetric patterns, which tend to appear more "natural," less synthetic. Examples of
these latter types are the Tiffen Vector-, Hyper-, North-, and Hollywood Star filters.
As with any filter that has a discrete pattern, be sure that depth of field doesn't cause
the filter lines to become visible in the image. Using small apertures, or short focal length
lenses make this more likely, as will suing a smaller film format, such as 16mm vs. 35mm
given an equal field of view. Generally, mid-range apertures or larger are sufficient, but test
before critical situations.
FILTERS FOR BLACK AND WHITE IMAGING
Tone Control Filters
Black and white imaging records only tonal differences between colored objects,
which appear as black, white, or different shades of gray. Proper rendition depends on
your own desires, and, for film, the differences between film sensitivity to colors and that of
the eye. The latter is due to the fact that most panchromatic emulsions used are more
sensitive to blue, violet and ultraviolet than to other colors. Therefore, blue appears as
lighter on film than it does to the eye. This can make a blue sky light enough to appear a
similar shade of light gray as the clouds that are in it, making the clouds "disappear." A
more "correct" cloud presence is obtained through the use of a yellow filter, such as a
Wratten #8, which can absorb blue light, darkening the sky to more closely match what the
eye would see. The #8 also acts as a general compensator for most subjects, giving a
tonal rendition similar to that of the eye. Deeper colors, further to the red end of the
spectrum, such as Wratten #15 deep yellow, #16 orange, and #25 and #29 red filters will
produce progressively deeper and artificially more dramatic renditions of blue sky.
Remember that, since these filters act on color differences to produce tonal
differences, the required colors must be present. The part of the sky you are recording
must be blue to be affected. Sky sections closer to the sun, or nearer the horizon, are
generally less blue than elsewhere. Use of a gradated neutral density filter can darken a
sky relative to the foreground, but will not increase contrast between a blue sky and the
clouds. In most situations where color-contrast and tone adjustment is involved, these
filters work similarly for black-and-white video as for film.
Using filters for contrast control can be a matter of artistic preference, or of
necessity. It is possible for two disparate colors, say a certain orange and blue, to record
as the identical tone, eliminating any visible difference between them. Filters will lighten
objects of their own color and darken those of their complement. Complementary color
pairs are: green-red; orange-blue; violet-yellow. An orange filter in the above case will