How to Learn Aperture in Photography

What is aperture in photography, and why should you care?

(Scroll to the end to see the video)

Webopedia defines aperture as the unit of measure that determines the size of the opening in the lens that can be adjusted to control the amount of light reaching the digital sensor. The size of the aperture is measured in F-Stops. An F-Stop is the international standard sequence of numbers that express the relative aperture. F-Stop is calculated by the “lens focal length” divided by the effective aperture diameter. Why should you care? Aperture does a lot for us in photography. As stated above, it lets in light or blocks light. So, it can make your exposure brighter or darker. Aperture can increase or decrease your “depth of field” which is how much of your image is in focus or not.

In this blog post and the corresponding podcast episode, I’ll walk you through how to do an exercise that will help you see for yourself how aperture works on a small scale, and then you can use what you learn there to discover how aperture works in the real world.

In this exercise (see video), you’ll increase and decrease the f-stop and see how that affects how much of your scene is in focus. We will let the camera control the other aspects of photography such as shutter speed and ISO. That way you can concentrate on learning how aperture can affect your image. I’m sharing this cheat sheet with you as a reference so you can see that a smaller number will make your pictures brighter, and a bigger number will make you images darker when in manual mode.

Example Situations

Action Sports
- We want to let as much light in as possible so we can increase our shutter speed. We will learn about shutter more next week. So, a small aperture value or a large aperture opening is usually what we want for capturing action such as f/2.8
- The side benefit is that we will have a shallow depth of field so that the subject is in focus and the background is blurry. Having a blurry background helps the subject stand out against an otherwise messy background.
Landscape Shots
- Generally, we want everything in focus for landscape. We might have horses in a vast scene, and we want every detail sharp. To get every detail sharp, we would use a big number or small aperture opening like f/22.
- Usually, the subject isn’t moving very fast, so shutter speed is ok to be slow. But, if the shutter speed is a concern, then you may wish to increase your ISO. We will learn about ISO in a couple of weeks.
Horse Portraits
- Generally, these fall in the middle apertures. The background is usually sufficiently far away, and we are relatively close to our subject, so the background will be soft even at f/7.1, for example.
- Lenses tend to be a little sharper at apertures that fall in the middle of the lens’ range.

Now, it’s your turn to practice. Watch this video below and listen to the podcast for details on how you can practice getting comfortable with the aperture at home!