Photoshop Elements Tutorial: Aspect Ratio and Print Size

by Erin on January 13, 2011 · 25 comments

Do you know the ONE setting you should change on your camera to improve focus?

My Photoshop Elements tutorial last week was about cropping versus resizing in PSE. You guys had lots to say about it, and as I anticipated, the tutorial bought up aspect ratio questions.

Oh, aspect ratio. Let’s knock that sucker out today, shall we?

Aspect ratio is the proportion of an image’s height to its width. Most of our cameras spit out images that are 2:3. This means that the height is 2/3s of the width. I’m so sorry to do this to you, but we really are going to have to talk algebra today.

Let’s think about an image that is 4 inches high by 6 wide. This is what most of our cameras give us – their aspect ratio is 2:3. How do I know that it has a 2:3 ratio? Well, I reduce my fractions. Does that bring some junior high nightmares rushing back to you ?

4:6 divided by 2 is 2:3 (4/2=2, 6/2=3). Are you still with me?

There are other common print sizes that share this ratio: 2×3, 4×6, 8×12, 16×24. How do I know that? Well, I multiplied 2×3 by 1, 2, 3 and 4 respectively. Note that 5×7 and 8×10 aren’t options in that list.

8×10 is another common print size. But it’s aspect ratio is 4:5. So, you could print an image with a 4:5 ratio as 4×5, 8×10, 16×20 or 24×30 with no cropping.

What about 5×7? Well, that’s just a weird one. It’s aspect ratio is 5:7. And we don’t really print anything else in that ratio. We don’t do 10x14s, that I know of anyway, or 15x21s. But if we did, they would all share the same proportion of height to width.

The last, and probably easiest to understand, is a square image. Its aspect ratio is 1:1. You can print them out as 1×1 inch squares, 12×12 inch squares, 5×5, or any other square. All without needing to crop. A square is a square, right?

An engineer from South Dakota asked why you have to crop to get a 5×7 from a 4×6. A 5×7 is larger, after all. Just add an inch horizontally and an inch vertically, and everything should be good, right?

But here’s the thing. A horizontal inch is 1/6 of the width, but a vertical inch is 1/4 of the height. So yes, you an add that extra inch to each side, but you have to stretch the image more up and down than you do side to side, and that gives you a distorted picture. Here is a 4 x 6 with a perfect square and a perfect circle:

And here is the same picture, stretched to fit a 5 x 7. We now have a rectangle and an oval. See the difference?

There are two workarounds to the distorted image issue.

You could print a 4×6 image onto a 5×7 piece of paper and have white space left around it, like this:

Not ideal, is it?

Or, you can crop off some of the 4×6 to make it have a 5:7 ratio, like the orange outline in this image.

The next topic in this topic is resolution. And my brain is frying just from writing this up. You must need a break too if you’ve really read this far, so I will save resolution for later.