a. Certain additive primary and subtractive primary colors are called "complementary colors."
Complementary colors is a term used to describe two colors that can be combined to produce white light.
Since all three of the primary colors must be present to produce white light, it is reasonable to assume
that we must combine the additive and subtractive colors that will provide the required amounts of these
wavelengths. For this reason, red and cyan (blue-green) are said to be complementary. Blue and yellow
(red-green) are complementary. Green and magenta (red-blue) are also complementary to each other.
The additive will transmit one-third of the wavelengths necessary, and the complementary will transmit
the remaining two-thirds of the wavelengths necessary to produce white light.
b. A filter passes its own color or colors that make up its own color but it does not pass the
complement of its own color. The exact effect of the filter is more clearly indicated by its number
identification and absorption curves than the color of the filter. Wratten numbers form the most
common numbering system for filters. The ability of a filter to absorb or pass certain colors gives you a
control to compensate for film limitations to emphasize one color, and to eliminate defects.
Filter compensation for film, limitations.
a. Correction filters adjust the color sensitivity of the film so that the picture will look more
natural. For instance, black and white film does not have the same sensitivity to all colors nor does it
respond in the same manner as your eye. If you use correction filters, your photograph will have a more
b. To make panchromatic (pan) or orthochromatic (ortho) film respond in daylight more like the
eye, use a yellow (No. 8) filter. No. 8 is the Wratten number. All film is generally sensitive to blue,
and daylight contains more blue than other colors. Thus, the reason for a filter is to reduce the amount
of blue that reaches the film in order to make the photograph appear more natural. A yellow filter is
used because it is the complement of blue and therefore absorbs the blue color. Table 1-1 is a list of the
more common filters used in black and white photography. At one time a combination of letters and
numbers was used to designate filters. Now most filters have only a number. The table shows the
obsolete designation and the new filter designations along with the colors.