Nikon Camera F3AF - Manual (Page 109)

EV RANGE OF CAMERA
The camera’s meter may be used only within the shutter speed
range covered by the exposure value (EV) range of the meter,
which varies with the aperture and ASA/ISO setting.
The charts on pages 68 and 69 show the reiationships between
the f/stop, shutter speed and fiim speed, indicating the usable
functioning shutter speed (for metering purposes) with any film
speed/aperture combination.
Careful attention to the following instructions will assure precise
exposure, automatically, over the complete exposure control
and meter range capabilities of your Nikon F3AF.
What Is EV?
Exposure value (EV) is a number representing the available
combinations of shutter speed and aperture that give the same
exposure effect when the scene brightness and ASA/ISO re­
main the same.
At ASA/ISO
too,
the combination of a one-second shutter
speed and an aperture of f/1.4 is defined as EV 1. If the aperture
is stopped down by one full f/stop or the shutter speed is one
step faster, the EV increases by one; if the aperture is opened
up by one full f/stop or the shutter speed is one step slower, EV
decreases by one. Using ASA/ISO 100 as an example, 1 sec. at
f/2 represents EV 2, 1 sec. at f/5.6 represents EV 5, while 1/125
sec. at f/5.6 represents EV 12. Because the exposure is the
same, 1/30 sec. at f/11 and 1/1000 sec. at f/2 both represent
EV12.
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