gested’’ exposure readings so that the proper expo-
sure for a given scene is recorded on film.
Exposure Settings
Aperture and shutters speeds are incremental in the
amount of the exposure they give on film. The
settings for aperture directly complement shutter
speeds, and vice versa. Each step in both settings
either doubles or halves the amount of light reach-
ing the film. These settings, known as stops, allow
the photographer to add more or less exposure in
even, predictable terms. For example, a shutter
speed of ½ second delivers twice as much light as
¼ of a second, but ½ second is half as much as 1
second, the next shutter speed up.
1 sec. 1/2 1/4 1/8 1/15 1/30 1/60 1/25 1/250 1/500 1/1000Common shutter speed settings. Moving left, each
number doubles the amount of light reaching the
film. Moving right, each number halves the amount
of light reaching the film.
Aperture settings, or f/stops, work in an identical
fashion. Aperture works by closing metal blades in
the lens to create larger or smaller openings. Each f/
stop number is based on the diameter of the aper-
ture blades in relation to the focal length of the
lens. Therefore, an aperture setting of f/22 repre-
sents a very small opening, and an aperture of f/2.8
is considered to be ‘‘wide-open.’’ For each increase
in aperture size, twice the amount of light strikes
the film. For each decrease, the amount of light is
cut in half, just as with shutter speeds.
f/2.0f/2.8f/4f/5.6f/8f/11f/16f/22f/32f/45f/64Common aperture settings. Moving left, each num-
ber doubles the amount of light reaching the film.
Moving right, each number halves the amount of
light reaching the film.
Each stop change, whether aperture or shutter
speeds, represents either a halving or a doubling of
the amount of light striking the film. For this rea-
son, photographers may use any number of combi-
nations of aperture and shutter speed to get the
same amount of exposure on film. This is called
the law of reciprocity. This law states that the am-
ount of exposure is the same, regardless of the rate at
which it is given. The classic analogy for this law is
the bucket analogy. If a full bucket represents a
good exposure, it does not matter if you fill that
bucket slowly, drop by drop, or quickly, with great
volume. The analogy to the amount of time repre-
sents the shutter speed, and the amount of water
allowed to leave the faucet represents the aperture.
Because of the law of reciprocity, a metered
exposure is given an infinite number of possibili-
ties. For example, a photographer can choose to
use a smaller aperture, provided that they compen-
sate the loss of light of the smaller opening with a
greater amount of time in their shutter speed. By
the same token, if the photographer wishes to use a
longer shutter speed, they must close down their
aperture an equal amount to compensate and still
achieve proper exposure. This is called reciprocal
exposure, or equivalent exposure.f/22@2 sec.
f/16@1 sec.
f/11@1/2 sec.
f/8@1/4th
Metered Exposure f/5.6@1/8th
f/4@1/15th
f/2.8@1/30th
f/2.0@1/60th
Equivalent exposure. Each setting will give the
exact same amunt of exposure on film as the me-
tered exposure.Bracketing is the term used to refer to deliber-
ately over- and underexposing the film, especially if
the photographer is unsure of the meter’s accuracy
for a particular scene. A typical bracketing method
is to overexpose by one stop (twice the amount of
light), and underexpose by one stop (half the
amount of light) from the meter’s recommenda-
tion. Because of equivalent exposure, this can be
accomplished either with change in aperture set-
tings or by changing the shutter speed.Minus one stop f/8@1/8thOR f/5.6@1/15th
Metered Exposure f/5.6@1/8th
Plus one stop f/4@1/8th OR f/5.6@1/4th
Bracketing. Subtracting one stop of light will have
the amount of light striking the film, resulting in
underexposure. Adding one stop will double the
amount of light striking the film, resulting in over-
exposure.The exception to the law of reciprocity on film
is when the exposure is very long or very short.EXPOSURE