There are three camera settings that are important to master if you want to be able to properly expose your images: ISO, aperture, and shutter speed. Last month we talked a little bit about the ISO setting on your camera. This month, we’ll explore aperture.

*Note: if you’re not comfortable using your camera in manual mode, don’t stop reading here! Your DSLR has an “aperture priority” setting which allows you to choose the aperture while the camera determines the other settings for you.

The aperture setting determines how wide the camera lens opens when you take a picture, and is usually expressed as an “f stop” such as f/2.8. Some people find aperture confusing because the larger the opening of the lens, the smaller the f stop number is. For example, f/11 is a very small opening and f/2 is a very large opening. The reason for this is that the numbers are actually fractions. 1/11 is smaller than 1/2. Therefore, f/11 is a smaller opening than f/2.

Clear as mud?

Just remember: smaller f stop number = larger aperture.

Why does aperture matter in achieving a correct exposure? The answer is light. Light is always the key to exposure and by controlling how wide your camera opens up when you press the shutter button, you are controlling how much light is getting in. If you have only a little light available to you (if you are indoors, for example), you will need to use a wider aperture to let more light in. If you are outside on a sunny day, you will be free to use a smaller aperture if you want to.

Here is an example of how aperture affects exposure. In these photos, aperture is the only setting that changed:

When choosing your aperture, it is important to remember that it determines the depth of field in your photos. In other words, it determines how much of your picture is in focus. Aperture is what lets us achieve the ever popular “blurry background” (you can learn more about that in this post), but as you make your aperture wider, the part of the picture that is in focus gets smaller. If you are taking a picture of a large group of people, for example, you don’t want to let your aperture get too wide or you will not have all of your subjects in focus.

So, as you experiment with your aperture setting this month, you will need to keep two things in mind as you chose your setting:

1) How much light is available to you? (Do you need a wider aperture to let in more light?)

2) How much of your picture do you want to be in focus? (Do you need a smaller aperture to get all the important parts in focus?)

Have fun practicing and next month we’ll tackle shutter speed!