What is 'aperture'?

The aperture of a camera is one of the things I think everyone should learn about when it comes to photography. It gives you the ability to control how sharp or blurry the background of a photo is.

To put it simply, it's the hole in the lens that the light travels through before it hits the camera’s sensor. When you change your aperture, you’re making this hole larger or smaller. The bigger the aperture the more light is let through and the smaller the aperture the less light is let through. A larger aperture will make the background of the photo blurrier and a small aperture will make the background sharper. A big aperture has a small number and a small aperture has a large aperture.

A lens with a large aperture

To get a little confusing (feel free to skim over this paragraph).. . Aperture is measured in f-stops and is written as a fraction f/8, f/2.8, f/11, etc. The 'f' stands for 'focal length' which means on a 50mm lens (a lens with a focal length of 50 millimetres) an f-stop of f/8 would mean the diameter of the aperture is 50 divided by 8 which equals 6.25 millimetres.

Below is a visual representation (not to scale) of the size of different apertures.

aperture diagram

To recap...

Large aperture:

  • Large hole
  • More light let through the lens
  • Blurrier background
  • Smaller number

Small aperture

  • Small hole
  • Less light less through the lens
  • Sharper background
  • Larger number

Below is an example of a shot taken at a large aperture so I could blur the mountains in the background.

A large aperture was used to blur the background of this photo

Here is a photo taken with a smaller aperture to make sure everything is in focus

A small aperture was used to make sure everything in this photo was sharp

 

 

What is 'Aperture Priority'?

The 'aperture priority' mode on your camera (often called Av mode) is a type of auto setting that lets you choose the aperture you want to use and the camera will figure the other settings out to expose the image. It's very useful if you want to have the camera quickly select the exposure for you or if you're in a scenario where the lighting is constantly changing (eg. fast moving clouds keep moving above you blocking the sunlight)

 

Which aperture should you choose?

It's up to you how you want your photo to look, I'd recommend planning the shot in your head before you take it and to decide how blurred or sharp you want the background to be. Choose your aperture on the feeling you want to portray to the viewer of the photograph, blurry backgrounds can have a nice soft look and can help direct the viewer's attention to an object that is in focus. On the other hand, having everything in focus might compliment the mood of the photo more. Experiment by shooting the same scene in with different apertures so you can get an idea of how they change the feeling of the image.

 

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