Nikon N4004s - Manual (Page 70)

EXPOSURE VALUE (EV)
Exposure consists of shutter control and aperture control.
The N4004S offers a range of speeds from 1/2000 second to 1
second, with each setting twice as fast as the next slower speed.
Faster speeds allow less light to pass; slower speeds admit more
light.
Aperture control enables you to vary the lens aperture opening
from large to small, with larger apertures allowing more light to
pass, and smaller apertures allowing less light to pass.
The standard aperture settings are ft .4, f2, f2.8, f4, f5.6, f8, f11,
f16, f22, f32, etc.
For simplicity, shutter/aperture gradations are uniform. A change
in shutter speed from 1/125 to 1/250 second, for example, re­
duces the light by 1/2. Similarly, changing aperture from f4 to
f5.6 reduces the light by 1/2. Each film used has a particular
sensitivity to light, indicated by the ISO number shown on the
film cartridge. To achieve the correct exposure for any particular
light value, the camera's Image Master Control adjusts the
shutter speed and aperture control so just the right amount of
light reaches the film to produce the correct exposure. That
amount of light is referred to as the Exposure Value or EV and
is assigned a number such as EV10, EV15, etc. The brighter the
light, the higher the EV number.
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