How aperture affects depth of field
In addition to helping control exposure, your aperture choice also affects what’s known as ‘depth of field’ (or DoF), as you can see in our latest photography cheat sheet above.
The depth of field is a measure of how much of your photo is in focus, both in front of and behind the point in the frame that you have actually focused on.
Depth of field is more apparent when your image contains elements at varying distances from your camera – and is particularly noticeable in the background.
Whether your background is sharp or out of focus depends on your aperture choice. For example, a wide aperture of f/4 will capture a shallow depth of field, so everything behind your focal point is more likely to be blurred (a great trick for portraits).
On the other hand, a narrow aperture – f/22, for example – will maximise the depth of field, often capturing everything from the foreground to background in focus (and is ideal for landscapes). You can see this effect in the sequence of images below.
The depth of field also varies depending focal length of your lens and how close you are to your subjects.
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