Aperture is the second component of the EXPOSURE TRIANGLE.
The aperture is the size of the hole through which the light passes on
the way to the film or sensor. Making
the aperture larger allows in more light.
Making the aperture smaller allows in less light.
Aperture is measured in ‘F stops’.
F2.8 is a wide aperture size. F32
is a narrow size. The larger the F-stop
number, the smaller the diameter of the aperture. The smaller the F-number, the larger the
diameter of the aperture.
When you press the shutter release button of your camera a hole opens
up that allows your cameras image sensor to catch a glimpse of the scene you are
wanting to capture. The aperture that you set impacts the size of that hole.
The larger the hole; the more light that gets in. The smaller the hole; the less light that
gets in.
Moving from one F-stop to the next doubles or halves the size of the
amount of opening in your lens (and the amount of light getting through). Opening up the aperture from F5.6 to F4
doubles the amount of light that hits the sensor. Stopping down the aperture from F11 to F16
allows half as much light on to the sensor.
A change in shutter speed from one stop to the next doubles or halves
the amount of light that gets in also. This
means if you increase the shutter speed one stop and decrease the aperture one
stop you let the same amount of light in.
Doing so does not change the exposure, but can have quite a different
effect on the image. This would change
the Depth of Field. Aperture not only
controls exposure (how bright or how dark an image is) but determines depth of focus – one of the most
creative tools available to the photographer. We will talk about that in another article.
There are numerous times you may want to select “Aperture
Priority”. Landscape photography is one
time when you may want the entire image in focus … Aperture Priority. In portrait photography typically, the
photographer wants the subject in focus and the background slightly blurry …
Aperture Priority. Macro photography
deals with capturing flowers, bugs, plants, etc. Often times the photography wants the subject
in sharp focus and the background blurred… Aperture Priority.
Setting your camera mode to “Aperture Priority” means you set the
aperture and the camera will attempt to deliver a good exposure. Some cameras signify
this with an "A" icon or "Av". Use Aperture Priority mode when you want to
control how much is in focus in front of and behind your subject. This ensures that the foreground to
the horizon is relatively in focus.
 |
| f9, 1/80 sec, ISO 100 |
The image above was captured with a small aperture. The foreground was a long distance from the
camera, causing the entire scene to be relatively sharp in focus.
The
image below was captured using a
larger aperture. But because the aperture was larger and the focal
point was relatively close to the lens, the foreground is in focus and
the distant
background is out of focus.
 |
| f8, 1/80 sec, ISO 100 |
In portrait photography it can be very handy to have your subject
perfectly in focus but to have a blurry background. This will ensure that your subject is the
main focal point and that other elements in the shot are not distracting. This leaves some to the imagination of the
viewer.
 |
| f5.6, 1/60 sec, ISO 400 |
Macro photographers tend to be big users of large apertures to ensure
that the element of their subject that they are focusing in on totally captures
the attention of the viewer of their images while the rest of the image is
completely thrown out of focus. Your camera’s “Portrait Mode” will attempt to blur
out the background. The camera will try
to use the fastest available lens setting (aperture). This sets a lens aperture
that’s wider than normal to blur backgrounds, and adjusts the image for a
softer, more flattering result. The
above image was captured with an aperture of F5.6, shutter speed of 1/60
second and an ISO of 400. These settings
are very common to use for portrait photography.
 |
| f5.6, 1/10 sec, ISO 400 |
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