Nikon f2 - Manual (Page 36)

EXPOSURE MEASUREMENT—continued
Exposure Control
The amount of light reaching the film plane is deter­
mined by a combination of the lens aperture and the
shutter speed. Since the two are interrelated, different
combinations will give the same exposure. A 1-step
change in the shutter speed, or a 1-stop change in the
aperture setting, will either halve or double the exposure.
For example, a shutter speed of 1/125 second passes
twice as much light as a setting of 1/250 second, and
only half as much light as a speed of 1/60 second; for an
aperture setting of f/11, twice as much light as f/16, and
half as much as f/8, is passed. This feature characterizes
the operation throughout the available range of shutter
speeds and aperture settings. With this in mind, it’s easy
to see that if a correct exposure for a scene is 1/125 at
f/11, then 1/60 at f/16 or 1/250 at f/8 will be equally
acceptable.
The best combination for your needs will depend on the
results desired. Use fast shutter speeds to freeze motion,
or use slow speeds to produce deliberate and creative
blur. Small apertures give greater depth of field, while
large apertures restrict sharp focus to the main subject.
The creative selection of both speeds and apertures will
greatly enhance your photography.
Metering Range
If the center “correct exposure” LED fails to illuminate,
even after all possible lens-aperture/shutter-speed com­
binations have been tried, then the available light is too
bright or too dim for the meter’s range. To correct this
situation, several measures may be taken, as follows:
Switch to a new film (either higher or lower ASA) that
more closely matches the available light; mount a neutral
density filter on the lens to decrease the light reaching
the film plane; or use artificial lighting (i.e., an electronic
flash unit) to increase subject illumination. Remember,
too, that the lens in use can greatly influence suitability
for bright or dim shooting. For example, a 50mm f/1.4
lens (with ASA 100 film) couples from EV —2 (f/1.4 at
8 seconds) to EV 17 (f/8 at 1 /2000 second) for excel­
lent low-light performance; on the other hand, a 200mm
f/4 lens proves more usable at bright-light levels, coupl­
ing (with ASA 100 film) from EV 1 (f/4 at 8 seconds) to
EV 20 (f/22 at 1/2000). Thus, choose the lens carefully
to match the existing lighting conditions.
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