Aperture, or f-stop, is the part of our exposure, that lets in varying amounts of light through our lens. The aperture is the opening in our lens that can be made larger or smaller.
The larger the aperture the more light we allow into the camera to make our exposure. Conversely, the smaller the aperture the less light gets in.
Here’s the counter intuitive part; the larger the f-stop number the smaller the lens opening and the smaller the f-stop number the larger the lens opening.
An aperture of f-4 lets in more light than an aperture of f-8.
Beyond adding more or less light, aperture is an important element in our compositions because it allows us to control something called depth of field.
Depth of field is the distance that remains in focus in the front of and in back of the actual distance that we are focused on.
For example if we are focused on ten feet the actual distance that is in focus may start at 7 feet and end at sixteen feet. In this case our depth of field starts at seven feet and ends at sixteen feet even though I am focused on ten feet.
So how can we use aperture to control depth of field? In brief, given the same lens/focal length and distance focused on, the larger the opening in the lens the less depth of field we will have; the smaller the opening of the lens the more depth of field we will have.
The two photographs below, taken during an aperture workshop to demonstrate depth of field during the meeting, should help illustrate this more clearly.
The compositions are nearly identical. The focal length of the lens remains the same as well as the distance focused on; I was focused on the Canon EOS camera for both photographs.
The top photograph was created with an aperture of f-4 while the bottom photograph was created with an aperture of f-8.
Notice the green bottle in the foreground and the clock in the background.
f/4
f/8
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