Aspect ratio is the ratio of the length of one side of an image to the other. The sensor in a digital camera (or the film format in a film camera) will have a “natural” aspect ratio determined by its size. For 35mm film, the aspect ratio was 3:2 (=1.5), and most DSLRs use the same. Some medium-format film cameras shoot square, or 1:1 (=1.0), images. Your E-PL5 has a 4:3 ratio, which gives the Micro Four-Thirds format its name. The 4:3 (=1.33) ratio is the same as “old-style” television, and is closer to square than the 3:2 (=1.5) DSLR ratio or the even wider 16:9 (=1.68) ratio of an HDTV.
Note: In some cases, people maintain the convention of keeping the horizontal dimension first (e.g. 4:3 for horizontal, or landscape, images, and 3:4 for vertical, or portrait, images). In other cases, they don’t, and think of aspect ratio as being independent of orientation (so a 4:3 aspect ratio could be in either landscape or portrait). Usually the meaning is clear from context.
While your camera has a natural aspect ratio, which is the starting point of your files, you can change the aspect ratio through cropping. The crop tool of Lightroom’s Develop module is accessed through the “dashed rectangle” icon above the Basic panel:
The crop tool lets you drag the border to crop the image. If the padlock icon is locked, the aspect ratio will be locked (so dragging a horizontal border also moves the vertical borders to maintain the aspect ratio, and vice-versa). If the padlock is unlocked, you can drag the borders independently, changing the aspect ratio.
In the Aspect drop-down, you can choose from widely-used aspect ratios like 4x5/8x10 (a common print size) and 2x3/4x6 (the famous 3:2 ratio of 35mm film and DSLR cameras). You can also add custom ratios and save them for re-use.
Why might we change the aspect ratio? There are a few reasons:
- As we’ll discuss in a future installment, photographic composition depends on exclusion as much as inclusion. If something is distracting, or doesn’t contribute to a scene, we often choose to exclude it. The decision to crop something out of the scene, while maintaining the elements we want to keep, may necessitate changing the aspect ratio.
- There’s a psychological component to aspect ratio. In horizontal (or landscape-oriented) photos especially, a wide aspect ratio can imply opennness, or a broad vista. It can create a dynamic space—for example, a space for the subject to look or move into. In contrast, a more square aspect ratio, like the 8x10 format, can feel intimate.
- Our eyes have a narrower vertical field of view than horizontal, so for vertical compositions, I feel that squarer aspect ratios, like the E-PL5’s natural 3:4, or even 8:10, work best.
And now, a rant: Lately, my Facebook feed is full of phone-camera shots in a 16:9 ratio, like HDTV. This is, presumably, the native sensor size of some phones these days. For horizontal compositions, 16:9 is sometimes a good choice. For vertical shots, however, it’s usually horrible. There’s typically a toddler’s head in the middle of the frame, and acres of pointless background above it. Whatever phone designer thought this was a good idea should be dragged out back and shot. If nothing else, the phone should default to cropping more square during vertical composition.
The conclusion: When cropping, don’t be beholden to your camera’s native aspect ratio. Try different aspect ratios to include or exclude the elements you want, and convey a sense of openness or intimacy to the scene.