Basic Photography Course

FILTERS FOR BLACK-AND-WHITE
PHOTOGRAPHY

Filters used with black-and-white film are classified

as contrast, correction, and special purpose. All contrast
and correction filters have a noticeable color. It is
important to note that a filter must be used with an
emulsion sensitive to the specific color of light it
transmits. Colored filters should normally be used with
black-and-white film only.

Special-purpose filters for black-and-white film

may be colorless, contain a hint of color, be noticeably
colored, or almost visually opaque. Some special-
purpose filters can be used with both black-and-white
and color film. Special-purpose filters are covered later

in this chapter.

Contrast Filters

Contrast filters are available in all colors and are

designed to exaggerate, reduce, or eliminate specific
colors of light. As their name indicates, these filters are
used to increase or decrease contrast in a negative that
provides differences between tones in the print.

To illustrate this, compare a red apple and a yellow

banana in a black-and-white print. With a red filter over
the camera lens, the apple appears lighter on the print
than the yellow banana. Both objects in this example
reflect the same intensity of light.

When you look through a red filter, the filter

definitely appears red. This color is the effect it produces
in your eye and the reason it is called a red filter. The
red filter is transmitting most of the red part of the
spectrum, some yellow, and some magenta. The color it
is not transmitting is cyan. If you think of this red filter

as an anticyan (blue and green) filter, you will better

understand the way it works.

When a red filter is used, most of the reflected red

light from the red apple is transmitted through the filter
and recorded as a dense area on the film. Only a portion
of the yellow light is transmitted, so it is recorded as a
less dense area on the film. Only some of the yellow
light is transmitted because the reflected light from the
banana consists of red and green light. Although the red
portion of the yellow light is readily transmitted through
the red filter, the green portion is absorbed to some
degree. Thus less light from the yellow banana reaches
the film emulsion.

When the negative is printed, the two print images

have separation in contrast because of the differences in
negative densities. The print image of the apple is lighter

than the print image of the banana because the negative
image of the red apple is more dense than the negative
image of the yellow banana.

When using a specific color of contrast filter to

provide separation between black-and-white images of
colored objects, you should also take into account what
effect the filter has on the images of other colored
objects in the scene. For example, when there are blue
and green objects in the scene, the red filter absorbs
some or all of the reflected blue and green light. The red
filter renders the negative images of these objects as
low-density areas. Thus the print images have darker
tones or densities.

Contrast filters can also be used to filter out an

image or filter out the image of a transparent stain on an
original document by copying it. This filtering-out
process takes place by blending or matching the density
of the image to be filtered out with the image density of
the surrounding area For example, to eliminate the
image of a yellow line on a white background, use a
yellow filter. The yellow filter should be as deep (same
color density) or deeper in color than the color of the
line. The yellow filter reduces the intensity of the light
reflected from the white background by absorbing blue
light. The intensity of the light reflected from the yellow
line is not greatly affected since the yellow filter readily
transmits the yellow light. The reduction of the intensity
of the light reflected from the white background and the
intensity of the light reflected from the yellow line
produces equal densities on the negative and thereby
does not render an image of the yellow line. Conversely,
when the yellow line is on a black background, a blue
filter does not allow yellow light to be transmitted.
Therefore, light from the yellow object is not allowed to
affect the film emulsion. Thus the line appears as a thin
area that matches the black background and is thereby
"eliminated"

Stains on a drawing or a picture can be filtered out

whenever the stain is transparent and reasonably pure in
color. The filter should be approximately the same color
as the stain. The stain may still show in the negative but,
in the case of line material, proper paper contrast and
printing exposure get rid of the rest of the stain image.

Remember, the color of filter required to eliminate

the image of an object or stain is determined by the color
of the object or stain and the darkness or lightness of the
surrounding scene area. Also, always use a filter that is

as deep or deeper in color than the color of the object or
stain to be eliminated. Refer to table 3-1 for clarification

on ways to use contrast filters.

3-2

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Basic Photography Course

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DOFMaster for Windows On-line Depth of Field Calculator DOFMaster for Mobile Devices On-line Depth of Field Table Hyperfocal Distance Chart Articles FAQ Recommended Books Support Contact Links Home As an Amazon Associate I earn from qualifying purchases.	contents <- previous page next page -> FILTERS FOR BLACK-AND-WHITE PHOTOGRAPHY Filters used with black-and-white film are classified as contrast, correction, and special purpose. All contrast and correction filters have a noticeable color. It is important to note that a filter must be used with an emulsion sensitive to the specific color of light it transmits. Colored filters should normally be used with black-and-white film only. Special-purpose filters for black-and-white film may be colorless, contain a hint of color, be noticeably colored, or almost visually opaque. Some special- purpose filters can be used with both black-and-white and color film. Special-purpose filters are covered later in this chapter. Contrast Filters Contrast filters are available in all colors and are designed to exaggerate, reduce, or eliminate specific colors of light. As their name indicates, these filters are used to increase or decrease contrast in a negative that provides differences between tones in the print. To illustrate this, compare a red apple and a yellow banana in a black-and-white print. With a red filter over the camera lens, the apple appears lighter on the print than the yellow banana. Both objects in this example reflect the same intensity of light. When you look through a red filter, the filter definitely appears red. This color is the effect it produces in your eye and the reason it is called a red filter. The red filter is transmitting most of the red part of the spectrum, some yellow, and some magenta. The color it is not transmitting is cyan. If you think of this red filter as an anticyan (blue and green) filter, you will better understand the way it works. When a red filter is used, most of the reflected red light from the red apple is transmitted through the filter and recorded as a dense area on the film. Only a portion of the yellow light is transmitted, so it is recorded as a less dense area on the film. Only some of the yellow light is transmitted because the reflected light from the banana consists of red and green light. Although the red portion of the yellow light is readily transmitted through the red filter, the green portion is absorbed to some degree. Thus less light from the yellow banana reaches the film emulsion. When the negative is printed, the two print images have separation in contrast because of the differences in negative densities. The print image of the apple is lighter than the print image of the banana because the negative image of the red apple is more dense than the negative image of the yellow banana. When using a specific color of contrast filter to provide separation between black-and-white images of colored objects, you should also take into account what effect the filter has on the images of other colored objects in the scene. For example, when there are blue and green objects in the scene, the red filter absorbs some or all of the reflected blue and green light. The red filter renders the negative images of these objects as low-density areas. Thus the print images have darker tones or densities. Contrast filters can also be used to filter out an image or filter out the image of a transparent stain on an original document by copying it. This filtering-out process takes place by blending or matching the density of the image to be filtered out with the image density of the surrounding area For example, to eliminate the image of a yellow line on a white background, use a yellow filter. The yellow filter should be as deep (same color density) or deeper in color than the color of the line. The yellow filter reduces the intensity of the light reflected from the white background by absorbing blue light. The intensity of the light reflected from the yellow line is not greatly affected since the yellow filter readily transmits the yellow light. The reduction of the intensity of the light reflected from the white background and the intensity of the light reflected from the yellow line produces equal densities on the negative and thereby does not render an image of the yellow line. Conversely, when the yellow line is on a black background, a blue filter does not allow yellow light to be transmitted. Therefore, light from the yellow object is not allowed to affect the film emulsion. Thus the line appears as a thin area that matches the black background and is thereby "eliminated" Stains on a drawing or a picture can be filtered out whenever the stain is transparent and reasonably pure in color. The filter should be approximately the same color as the stain. The stain may still show in the negative but, in the case of line material, proper paper contrast and printing exposure get rid of the rest of the stain image. Remember, the color of filter required to eliminate the image of an object or stain is determined by the color of the object or stain and the darkness or lightness of the surrounding scene area. Also, always use a filter that is as deep or deeper in color than the color of the object or stain to be eliminated. Refer to table 3-1 for clarification on ways to use contrast filters. 3-2 contents Basic Photography Course <- previous page next page ->	As an Amazon Associate I earn from qualifying purchases.
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