The Aperture
The hole that lets light into the camera from the lens allow a great deal of control
over how the picture looks.
Aperture settings can be a bit confusing. They are usually written in the form
f/2. Without worrying where the f/ comes from the number gives an indication
of how wide or narrow the aperture opening is. Slightly confusingly, a small
number indicates a wide aperture, large numbers vise-versa.
So why play with the aperture apart from using it to allow you to get the shutter
speed you want? The aperture controls a property called the 'depth of field'
(not to be confused with depth of focus - see lenses). This is the range of
distances from the camera over which subjects will look sharp.
For landscape photography it is common to use a small aperture (high f-number) because
this keeps things in focus both close to and far away from the camera e.g. the tree
nearby and the mountains in the distance.
Examples
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A realtively small aperture (large f-number) keeps both the shore in the forground
and mountains in the distance sharp in this picture. |
If you want to pick your subject out from the background you can use a wide aperture
(low f-number). With this set up, the subject you have focused the camera
on will be sharp and things in front of or behind it will be blurred. The
wider the aparture the more extreme the effect.
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A wide aperture (f/3.5) picks this duck out from the background and forground.
Without this the duck might be lost against clutter in front of and behind it.
Also, because the aperture is so wide some parts of the duck are better focused
than others. |
Aperture Priority
Most modern SLR cameras have an aperture priority mode. You select the aperture
setting that you want and let the camera work out what shutter speed to use to get
the correct exposure. If you set a very small aperture bare in mind that the
camera will have to use a very slow shutter and you might get blurred pictures.
This mode is useful if you have a certain depth of field in mind for a picture (see
examples above), but don't want to have to mess around with the shutter setting
every time you alter the aperture.
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