c. Orthochromatic film records green, blue, and ultraviolet light but not red. Therefore, reds
appear dark on the prints.
d. Panchromatic B film records some red as well as green, blue and ultraviolet light. It is fairly
close to the eye in color sensitivity. The natural color rendition makes it useful in close portraits and
copy work involving multicolors.
e. Panchromatic C film records more red than panchromatic B, making the reds print a lighter
shade of gray. The greater contrast between clouds and sky makes panchromatic C useful for scenery.
f. Infrared film is sensitive to ultraviolet and blue light, as are all films. It is also sensitive to
the wavelengths longer than those visible to the eye, called infrared. Since infrared films are sensitive to
light beyond the visible light, the film is used to see what cannot be seen by the human eye. For
example, artificial trees used as camouflage appear darker than live trees when photographed with
infrared film. It is also used for investigative types of work.
Learning Event 2:
FILM SPEEDS AND CONTRAST
1.
Selecting film speeds.
a. Film speed is given as an International Standards Organization (ISO) rating. In the past it
was known as American Standards Association (ASA) rating. This rating, much like the octane rating of
gasoline, determines how much light is required to obtain an acceptable exposure. Normal film speed is
about ISO 100.
b. Fast films have ASA/ISO ratings well above 100, even up into the thousands. The fast films
allow you to use very fast shutter speeds to stop the action and photograph moving objects. Also, since
less light is required for fast films, a slow shutter speed used with the fast film permits photographing
under poor lighting conditions. Fast films are not normally required for copy work.
c. Slow films under ASA/ISO 100 should be used for copying. They usually have a finer grain
and produce enlargements with excellent detail and little grain.
2.
Contrast is the range of tones.
a. Normal contrast film is most commonly used because it reproduces white, black, and all
shades of gray.
b. When the material to be copied has a constant tone, that is, very little contrast, with little
difference in color, then use a high contrast film to make the light colors lighter and the dark areas
darker.
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