ChApter 3. Controlling exposure
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Exposure Controls—The shutter and Aperture...
The most important exposure controls on your camera are the shutter speed
and aperture because both affect the total amount of light reaching the image
sensor. However, they do more than just control the exposure. As you’ll see
shortly they can also be the most creative controls you have.- The shutter opens to begin an exposure and closes to end it. The shutter
speed setting determines how long the shutter remains open to expose the
image sensor. - The aperture is the hole through which light enters the camera. Its size
can be changed to control the brightness of the light allowed through to the
image sensor.
If you strip away all of the modern technology and look at the earliest cam-
eras, you will find the same controls in much simpler, and perhaps easier to
understand, versions.
In the early days of
photography, a plate
called a waterhouse
stop, was inserted
into a slot in the lens.
Selecting one of the
holes was much like
selecting an f/stop
today. A lens cap was
removed and then
replaced to begin and
end the exposure—a
primitive version of a
shutter. This vintage
camera is surrounded
by waterhouse stops
(apertures) and a lens
cap (the shutter) leans
against it.
Less light makes an
image darker (left) and
more light makes it
lighter (right).
It’s not just old cameras
that use waterhouse
stops. The Lensbaby,
“a selective focus SLR
camera lens”, comes
with four apertures you
can insert into the lens.