The term "Aperture" actually refers to the size of the aperture (an adjustable hole that
light passes through on its way through the lens). The photographer can change the size
of the aperture with controls on the camera body, or with a ring at the base of the lens (on
older cameras).
Apertures are sometimes called "f-stops", and are usually written with a script "f" in
front. Watch out – small numbers mean big apertures, and big numbers mean small
apertures! (For instance, f2.8 is bigger than f16.) Each number in the series is considered
to be 1 "stop" different than the last, allowing 1/2 as much light into the camera.
Some lenses "stop down" to different apertures than others. Zoom lenses usually have a
lower aperture range than "prime" (non-zoom) lenses. Low magnification lenses usually
include bigger aperture settings, and high magnification lenses usually include smaller
ones.
Aperture Fact #1
The smaller you make the aperture, the less light can come through the lens. You
may have to balance a small aperture setting with a slower shutter speed to allow
the right amount of light into the camera, and vice versa. (More on this later!)
Aperture Fact #2
Regardless of where you focus the lens, more of
the photograph will appear sharp and clear if
you use a smaller aperture. To see this for
yourself, make a pin-hole in a piece of paper
and look through it. Focus your eye on
something far away and hold a finger out in
front of you. Keep your eye focused, and take
the paper away. Notice how much blurrier your
finger looks without the narrow hole! This is
why controlling the aperture size is important –
you can choose to make the whole picture sharp and clear, or to make most of it
blurry and have only your focus point stand out.
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