haze filter includes contrast and correction filters. When
contrast and correction filters are used for haze
penetration, they may be considered special-purpose
filters. Although contrast filters can be used for cutting
haze, these filters affect the gray tone rendering of
colored objects. The contrast and correction filters that
absorb the shorter wavelengths are the most effective.
The recommended contrast and correction filter colors,
in the order of greatest to least effective for haze
penetration, are as follows:
The use of an infrared sensitive black-and-white
film with an infrared filter provides the greatest haze
penetration of all. Special, visually opaque infrared
filters completely absorb the scattered ultraviolet
radiation and the visible light that produce haze. This
absorption by an infrared filter allows the scene to be
photographed entirely with unscattered infrared
radiation. An infrared sensitive black-and-white film
without an infrared filter, or at least a red contrast filter,
is not effective for haze penetration. Infrared
black-and-white film is sensitive to ultraviolet radiation,
violet, and blue light as well as infrared radiation and
red light. The gray tone rendering of a colored subject
in a black-and-white print produced from an infrared
negative is greatly distorted or contrasty.
The visually opaque infrared filters are identified by
numbers as follows:
When the effect of haze is to be reduced with an
equal change to the gray tone rendering of all colored
objects in a black-and-white print, filters that primarily
absorb ultraviolet (UV) radiation are required. These
filters have a very pale pink or yellow tint and may be
identified by numbers as follows:
Colorless haze or ultraviolet absorbing filters are
often used to protect the front element of a lens from
damage. It is much cheaper to replace a filter than it is
to repair or replace a lens.
The polarizing filter is another type of special-
purpose filter that can be used to reduce the effects of
Polarizing filters look like gray neutral density
filters. However, their effect becomes apparent when
you look at the blue sky through a polarizing filter while
rotating it. As you rotate the filter, the sky appears to get
darker, then lighter.
Polarizing filters are used in black-and-white and
color photography for the following reasons:
1. Reduction or elimination of unwanted
reflections (glare) from nonmetallic surfaces, such as
glass and water
2. Exposure control, similar to ND filters
3. Reducing the effects of haze
4. Darkening the blue-sky image in both black-
and-white and color photography
5. Increasing color saturation in a color photograph
without altering the hues of image colors
As discussed in chapter 1 of this training manual,
the term polarize refers to a property of light that cannot
be seen-the direction in which light rays vibrate.
Unpolarized light rays vibrate in all directions at right
angles to the ray itself. A light ray is polarized when
vibrations are in one direction only.
Any synthetic material that polarizes light may be
called a polarizer, or polarizing device. A polarizing
screen is a polarizer in sheet form.
There are a number of different polarizing filters.
However, there are only two main types: one type fits
over the camera lens and the other is designed to be used
over a light source. Since they do not affect color,
polarizing filters and screens may be used for both
black-and-white and color photography. A polarizing
device used over the camera lens may have small posts
(known as indicator handles) projecting from the rim for
aligning the axis of the polarizing grid.