Home Photography Lessons Beginner What is Aperture? Introduction Lesson

What is Aperture? Introduction Lesson

In our course on Understanding the Exposure Triangle, we talked about the importance of light in photography and about controlling how much light gets exposed to the digital sensor in your camera to produce an image. You learned how ISO, along with the aperture setting and the shutter speed control how much light enters the camera to make you image. These three pillars work together to control lightness or darkness of a photograph.

Today we’re going to talk specifically about aperture.

Introduction to Aperture

Aperture is the opening in the lens through which light passes to the camera and is measured in f-stops (or stops) usually ranging from 1.2 to 32. Inside the camera lens is a mechanical iris diaphragm that controls the amount of light transmitted to the imaging sensor in the camera. The diaphragm stops the passage of light, except for light that passing through the opening (or the aperture). It’s a lot like the shades on a window control the light.

Charles Bryant created a great video clip that will teach you the basic principles of aperture.

Understanding Aperture in Photography (Video)

We love this quirky 36 second video from Canon Australia that briefly describes aperture.

Aperture plays two important roles in photography. First, it limits the amount of light that passes through the lens so you get a properly exposed image. When you change the f-stop value, you change the opening of the iris. The lower the f-stop, the larger the opening (just the opposite of what you might expect). Second, it controls the depth of field (which is the range in an image that is in focus). Another way to explain Depth of Field is the area of sharpness in front of and behind the subject you’re focused on.

What is Aperture

Moving from one f-stop to the next (up or down) doubles or cuts in half the amount of light passing through the lens. A smaller f-stop number like 2.8 means a larger opening of the iris. When you change the aperture from a 2.8 to f4, its called stopping down. Lenses have a range of apertures and lenses do not have all apertures available. When we say a lens is a 2.8 lens, that means the lowest aperture available is 2.8. In the diagram above you can see f-stops of; 1.4, 2, 2.8, 4, 5.6, 8, 11, 16, 32.

Changing the aperture is usually a setting inside your camera.

The Basics of Aperture (Free Video)

This entertaining 6 minute video on The Basics of Aperture by Larry Becker at B&H Photo goes into a little more detail on the mechanics of aperture.

Measuring Aperture

Aperture is measured in f stops. The larger the number under the f, the smaller the hole (aperture) and the less light that comes in.

How Aperture Affects Depth of Field

A wide open aperture results in a shallow depth of field whereas a smaller aperture results in a great depth of field. If you want to know why this is see our lesson on the physics of depth of field. If you’re interested in knowing what the “f” is about in all the aperture settings see our lesson on “aperture f number“.

Aperture Photography Course from Udemy

Master the Aperture Mode on your Digital SLR Camera

Master the Aperture Mode on your Digital SLR Camera
Improve your photography by mastering the aperture mode and learning all there is to know about the aperture mode.

Photography Course
Photography Coursehttps://photographycourse.net/
Photography Course offers free courses, tutorials, tips, and tricks for photographers of all skill levels. Browse our collection of courses from photographers all around the world to take your passion to the next level.


  1. This really helped me a great deal. I have enjoyed taking pictures since I was a teenager and just recently decided to really study it. Thanks for the videos.

  2. If there is anyone in Edmonton, AB who may see this comment and would be willing to help me with I would appreciate it if you would message back to me..thanks. Bonnie

  3. Thank you for reminding me of techniques from many years ago with film cameras. Want to get back into the relaxing interests that gives me peace of mind, including digital cameras. Keep up good work.


Please enter your comment!
Please enter your name here

This site uses Akismet to reduce spam. Learn how your comment data is processed.

Must Read

See Better

Seeing Photographs with Better Eyes The psychology of seeing and how it affects composition. Your eye (and lens) sees something, but your eye is connected to...

Platypod Review – Is it the Best Compact Tripod?

The search for a light-weight, portable, yet sturdy tripod is over! If you’re looking for an unconventional tripod alternative, you...

Digital Photography Course by Stanford Professor

We are constantly on the lookout for free quality photography education and training resources, and we found an outstanding series of Lectures on Digital...

Wildlife Photography Tips for Beginners

5 Wildlife Photography Tips Thinking about trying your hand at wildlife photography? Check out these great tips for shooting stunning, dynamic wildlife images -- even...

Digital Photography Tip: Crop for Impact

Crop for Impact Farmington Bay Waterfowl Management Area near Salt Lake City has ideal winter conditions, which often attract hundreds of bald eagles. Every eagle...
Cart Item Removed. Undo Have a coupon ?
  • No products in the cart.