How Image Aspect Ratios Work in Digital Photography

Many amateur and even professionals photographers are still confounded by the cropping results caused by certain image aspect ratios. You can’t always have your 8×10 prints without sacrificing at least two inches from the original image. Why? Because it’s a 4:5 aspect ratio. This time we are revisiting image aspect ratios. If you’re a photographer with a nebulous distinction between image aspect ratios and the final print, then this article is for you.

Image Aspect Ratios: What the Heck Are They?

Simply put, an image aspect ratio determines the crop of your print. Common DSLR cameras have aspect ratios of 3:2 and 4:3. We’ll find 5:3 and 4:3 aspect ratios in medium format cameras. Let’s look at one of the most common image aspect ratios, 3:2. If this is your camera’s aspect ratio, expect to loose a couple of inches on sizes such as 8x10s. The 3:2 ratio will produce an 8×12 image/print size instead. To determine this size, simply choose any number and multiply it by your image’s aspect ratio. In the case of a 3:2 aspect ratio, I multiplied each number by 4. The result is 8×12. Repeat this simple multiplication for other sizes. Make sense?

Finding Your Image Aspect Ratio

Step 1: Open the Image Size Dialog Box | One way to figure out your image aspect ratio is to bring an original image into Photoshop. Don’t crop! Once in Photoshop, go to Image > Image size, or use the keyboard shortcut Ctrl+Alt+I (Win) or Cmd+Opt+I (Mac). Ensure that the only selected check box is Constrain Proportions and set the Resolution to 72.  Don’t adjust the Width and the Height. They are automatically controlled by Resolution.

Image Aspect Ratios

Step 2: Set the Resolution | Set the Resolution to 300 and check the Resample Image box. Notice the change in the Width and Height fields. These two values are parallel to your sensor’s megapixels, unless you’ve altered the size of your image prior to this exercise.

Image Aspect Ratios

Step 3: Check Scale Styles & Set the Width |  Once you’ve completed step 2, check the Scale Styles box and set the Width to 3. In my case, the Height automatically changed to 2 . This implies that the aspect ratio of my camera is 3:2. What is yours?

Image Aspect Ratios

Note: As you know, in this exercise we used a 3:2 ratio. This image aspect ratio will give us us full frame prints in the following sizes: 4×6, 6×9, 8×12, 10×15, 12×18, 14×21, 16×24, 18×27, 20×30, and so on. Simply multiply a single number by each aspect ratio number, and you’ll have a better understanding of  how to crop, or not crop, your images for print.

Image Aspect Ratio in Camera Raw

Those of you who process images through Camera Raw, don’t forget to set the image aspect ratio when cropping. Skipping this step may result in undesirable cropping results during print production. For example, if you’ll be printing a 20×30, set the image aspect ratio to 2×3, as demonstrated below. Remember the simple multiplication: 10×2=20 and 10×3=30. This is why the 2 to 3 ratio is the right choice.

Camera Raw Image Aspect Ratio

Image Aspect Ratios in Photoshop CS6

In Photoshop, select the Crop Tool, or use the shortcut key command C, and navigate to the cropping menu at the top. From the drop down list an image aspect ratio can be selected. Use Size & Resolution to determine and create your favorite sizes as presets.

Imae Aspect Ratio in Photoshop CS6

Image Aspect Ratio in Lightroom

There are similar options in Lightroom. Bring an image into the Develop module and select Crop Overlay, or use the keyboard shortcut R. Make a selection from the presets or enter a custom image aspect ratio by selecting Enter Custom…

Lightroom Image Aspect Ratio

Your Thoughts

In the past I’ve worked with both amateur and professional photographers who barely understood image aspect ratios. What about you? Is this piece of knowledge a second nature to you, or is it something completely new? Be the first to share your thoughts in the comments are below.

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