When you first ventured into the field of photography and, in particular, post-processing your images to get them ready to share on social media or to print, you probably found yourself wondering, what is aspect ratio? And, how does it affect my photos?

This guide will define aspect ratio, explain why it’s important, describe the common aspect ratios and what they’re used for, and tell you how to choose the appropriate one for your photo.

The aspect ratio you use for your images affects the composition.
Photo by Mika Baumeister on Unsplash

What is aspect ratio?

Remember learning about ratios in grade school math class? They represent the relationship between two numbers. In photography, the aspect ratio represents the relationship between the width and the height of an image. In essence, that defines the shape of your image, whether it be square, rectangle, or panoramic.

Aspect ratios are written as two numbers separated by a colon with the width written first. For example, an image that is 3 times as wide as it is tall is said to have an aspect ratio of 3:1. A square image is the same width and height, so its format is 1:1.

It’s important to understand that the aspect ratio does not define the actual pixel size of your photo—just the format. To demonstrate, a square 500 x 500 pixel image and a 2,000 x 2,000 pixel image both have the same 1:1 format even though they are very different sizes.

Different aspect ratios

Why is aspect ratio important?

Aspect ratio has a major influence on the composition of your photographs. Take another look at the example image above. See how the different formats on the right-hand side change the composition of the image? Which one do you think is most successful for this particular image?

Aspect ratio is also important is when it comes to printing your photographs. Your format needs to match your print size or parts of the image will be cropped off and the composition will be changed. If you plan to print your photos, consider your final print size when choosing your aspect ratio.

Common aspect ratios

These are the common aspect ratios you will encounter in photography today:

  • 3:2 – This is the most popular aspect ratio because it’s the format of traditional film and has been the standard for many years. Most DSLR, mirrorless cameras, and point-and-shoot cameras use this by default.
  • 4:3 – This format is used by most smartphones, some point-and-shoot cameras, and Micro Four Thirds cameras.
  • 16:9 – This is a very common format for video and is gaining popularity for photography because it’s the most common aspect ratio for modern computer and television monitors.
  • 5:4 – This is the format to use when making 8×10” and 16×20” prints of your images.
  • 3:1 – This is the common aspect ratio for panoramic images.
  • 1:1 – Square format images were popularized by social media but are gaining in popularity in print media, too.
Panoramic images often have an aspect ratio of 3:1.
Photo by 家鸽 on Unsplash

Aspect ratios and common print sizes

We mentioned above that your final print size is affected by the aspect ratio of your image. So, it’s helpful to know what potential print sizes you can use with each format. Here’s a list of the common aspect ratios and some common print sizes (in inches) for each.

  • 3:2 – 4×6, 6×9, 8×12, 10×15, 12×18, 16×24, 20×30, 24×36
  • 4:3 – 6×8, 9×12, 10×13, 12×16, 18×24
  • 16:9 – no common print sizes
  • 5:4 – 4×5, 8×10, 11×14, 16×20
  • 3:1 – 4×12, 5×15, 8×24, 12×36
  • 1:1 – 5×5, 8×8, 10×10, 12×12, 16×16, 20×20

How to adjust the aspect ratio

If you want to change your aspect ratio, you can do it one of two ways, either in-camera or in post-processing. Let’s discuss both.

Adjusting in your camera

As we mentioned above, most cameras come with a default aspect ratio, usually 3:2. However, many DSLR and mirrorless cameras allow you to change it before you shoot. You’ll need to refer to your camera’s user manual to determine if you have this feature and find instructions on how to do it. Usually, the aspect ratio is easily changed from within the camera’s menu function.

Adjusting in post-processing

You can easily change the aspect ratio of your photograph after it’s taken by cropping the image in photo editing software like Lightroom, Adobe Camera Raw, Photoshop, or one of these free photoshop alternatives. Simply choose the crop tool in whichever app you’re using.

When cropping your image in post-processing, however, you should avoid freehand cropping. Instead, select an aspect ratio or image size from the crop settings before you crop.

You can easily adjust your aspect ratio in post-processing.
Photo by Szabo Viktor on Unsplash

How to choose your aspect ratio

Quite a bit of thought should go into your reasoning for choosing a particular aspect ratio or cropping to a particular format. Before you ever snap your photo, it’s important to keep in mind what you’ll use the image for. Will it be primarily used on social media? Will it be printed and framed?

This is important because, as you saw in the list above, different common print sizes use different aspect ratios. What’s more, the most common sizes of printing paper and photo frames don’t match the most common aspect ratio! The best way to work around this is to determine what size you’ll print upfront and then shoot with that format in mind. Of course, that’s not always possible. So try to shoot with enough space around the edges that you can crop later if you must. Or, shoot multiple images at different aspect ratios.

Even if you’re only planning to post your images online, the different social media apps use different aspect ratios. Instagram and Facebook mages look best in 1:1 format (but they do now allow other sizes), while Pinterest uses 2:3 and YouTube uses 16:9. And these are constantly changing. So, shoot for the sites you know you’ll be sharing your images on.

Final thoughts

While aspect ratio is a fairly simple concept to understand, it’s also extremely important to consider in your photography. It has a dramatic impact on the composition of your image but also affects how you’re able to output your work, whether via print or online.