Introduction to Aperture in Digital Photography

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What is Aperture?

Aperture is ‘the size of the opening in the lens when a picture is taken.’

When you hit 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’re 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.

Aperture is measured in ‘f-stops’. You’ll often see them referred to here at Digital Photography School as f/number - for example f/2.8, f/4, f/5.6,f/8,f/22 etc. 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). Keep in mind that 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 one and decrease the other you let the same amount of light in - very handy to keep in mind).

Depth of Field and Aperture

There are a number of results of changing the aperture of your shots that you’ll want to keep in mind as you consider your setting but the most noticeable one will be the depth of field that your shot will have.
Depth of Field (DOF) is that amount of your shot that will be in focus.



Large depth of field means that most of your image will be in focus whether it’s close to your camera or far away (like the picture on top where both the foreground and background are largely in focus - taken with an aperture of f/22).

Small (or shallow) depth of field means that only part of the image will be in focus and the rest will be fuzzy. Aperture has a big impact upon depth of field. Large aperture (remember it’s a smaller number) will decrease depth of field while small aperture (larger numbers) will give you larger depth of field.

The first picture on the left was taken with an aperture of f/22. The f/22 picture has both the flower and the bud in focus and you’re able to make out the shape of the fence and leaves in the background.



The f/2.8 shot has the left flower in focus (or parts of it) but the depth of field is very shallow and the background is thrown out of focus and the bud to the right of the flower is also less in focus due to it being slightly further away from the camera when the shot was taken.

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