Long, long ago, in the before time, there was the 35mm camera. The 35mm camera produced images with an aspect ratio of 4 x 6 or 6 x 4. And so it was, and so it continued to be, until some numbskull invented the digital camera and decided that the standard aspect ratio was going to change. So what is aspect ratio and why do you need to worry about it? Read on to find out.
In simple terms, aspect ratio is the proportional difference between the width and height of an image. A 35mm camera has an aspect ratio of 6:4. Other cameras have an aspect ratio of 4:3. And to further complicate matters, not all digital cameras use the same aspect ratio, and some of them only have a single aspect ratio, while others allow you to change the aspect ratio. Modern iPhones, for example, will let you should shoot in a square format as well as a 16:9 format. And if you decide you don't like either one of those, you can use an app to crop the image to whatever size you like.
If your photo is strictly going to remain digital, the aspect ratio doesn't really matter that much. However, if you plan to print it out on photo paper, you may run into some problems if you cropped it in post-processing or used an aspect ratio that isn't standard.
"Full frame" vs. "crop sensor"
You may have heard the term "full frame camera," which is the digital equivalent of a 35mm camera. Most professional model DSLRs are full frame, and some higher-end consumer models are as well. You may also hear these cameras referred to as "FX." Full frame or FX cameras use the 3:2 aspect ratio, which corresponds to that 6 x 4 print size.
Most digital cameras fall into a second category, sometimes called a "crop" sensor because they are essentially a cropped version of a full frame image. Some crop sensors, the common APS-C, for example, also use the 3:2 aspect ratio. Others, like the smaller micro 4/3rds models and compact "point-and-shoot" cameras, use a 4:3 aspect ratio. The 4:3 aspect ratio corresponds to a printed size of 4.5 x 6, and that's where the trouble starts--if you try to print a 4:3 image at the standard 4x6 size, you'll lose about a half inch on the short side of the photo.
It's probably not a coincidence that the 4:3 aspect ratio is the same one used by standard-sized televisions and computer screens. That's likely the reason why it was chosen as the aspect ratio for digital cameras--because it precisely matched the aspect ratio of the most popular monitors in use at the time.
Other aspect ratios
As I mentioned earlier, not every camera forces you to stick with a single aspect ratio. For example, most smart phone cameras will give you the option to shoot at the 1:1 aspect ratio, which is a sort of novelty size that’s popular on Instagram and other photo-sharing applications. Shooting square is trendy but can prove problematic if you ever decide to print those images. If you do shoot in the square format, just remember that you will need to do some post-processing to those images before they become printable, because the cropping will be pretty severe if you try to send them to the printer as-is.
Smart phones also shoot at the 16:9 aspect ratio, which is considered the "panoramic format.” The longer 16:9 aspect ratio lets you stitch together multiple images in post-processing so you can include a much broader view of a scene. Of course, panoramics are really all over the place in terms of aspect ratio—many panoramic photographers will print images that have even longer aspect ratios, and they may even stack photos both vertically and horizontally. But generally speaking, the 16:9 aspect ratio tends to feel the most comfortable and fits with the panoramic style much more naturally.
When does aspect ratio matter?
Aspect ratio does matter for some applications. If you're shooting landscapes, for example, the aspect ratio can impact the visual balance of your photographs. That’s one reason why most landscapes that are shot in that 3:2 orientation are shot horizontally, because it’s easier to use the rule of thirds to compose a horizontal 3:2 image. If you use the rule of thirds to shoot a landscape photograph in the vertical orientation with a 3:2 aspect ratio, you'll likely end up with an image that has way too much sky or way too little sky depending on which third you place the horizon. Does that mean that you should switch to the 4:3 image format for vertically composed landscapes? Not necessarily, but you do need to keep that limitation in mind and frame your image a little differently because you’ll probably want to crop to the 4:3 aspect ratio in post-processing.
Now, when you're printing photographs, you may be tempted to just crop off as much of the photo as makes sense for that particular composition. And if you're only going to be displaying that photograph in digital format I would say that you are correct in making that call. However, if you plan to print your image, it is best to stick to one of the standard aspect ratios. For landscapes, you may choose 2:3 (which again corresponds to a print size of 4x6), but you can also choose 5:4, which was the aspect ratio favored by many of the old-time landscape photographers who shot with large-format cameras. The 5:4 aspect ratio also corresponds to the standard print size of 8 x 10, so if you crop to 5:4 it will be a lot easier and less expensive to purchase mounting materials for the image because you won't have to have them customized. You can also use the 7:6 aspect ratio, which was used by many medium format film cameras back in the days of film. The 7:6 aspect ratio corresponds to the popular 12 x 14 size, which makes for a good sized print that can also be mounted using standard materials and frame sizes.
Remember that if you're going to be printing at those larger sizes, you probably will want to shoot in RAW. Shooting in RAW format ensures that your camera captures all of the detail that its sensor is capable of capturing. That way when you crop the photographs to those standard sizes, you're not losing too much resolution, and you'll still be able to print the image at those larger sizes without worrying about image quality. Hint: if your resolution drops below 300 dpi, you should not print the image at the larger size because some pixelization will start to become obvious.
Now keep in mind when you're shooting images that you plan to crop and/or print at large sizes that you need to take that cropping into account when you frame them in your viewfinder. It's a good idea to have a rough visual feel for that aspect ratio so that you can make sure that you're not going to crop out anything important from the original image.
Which aspect ratio should you choose?
Try to stick with one of the standard aspect ratios because it'll be less of a headache when you have the image printed. But if you do feel like you must use an odd size, remember that the cropped image needs to fit within one of those standard sizes when the photograph is printed. For example, if you crop your image to 4x4, you can print it on a 4x6 piece of photo paper, but you’ll have a one-inch white strip on opposite sides of the print that you’ll have to physically crop out with a pair of scissors or chopper after you get the print back. It also means buying custom mounting materials, which can be expensive, so keep that in mind as well.
Each aspect ratio has a different appeal and personality, so try to fit the subject to the size. Remember, for example, that a horizontal 4 x 6 image of a landscape is going to look pretty natural, while the aforementioned 6 x 4 vertical orientation is going to have a little too much sky or a little too much foreground. When shooting a vertical landscape, you may want to choose the 4:3 aspect ratio or the 5:4 aspect ratio instead, which will eliminate that problem. A 7:6 aspect ratio (or a 12 x 14 print), on the other hand, may be a better alternative for a macro photograph of a symmetrical object.
Ultimately, the aspect ratio decision is up to you, and it really depends on the subject matter and how well you think it will represent at the aspect ratio you've chosen. The one thing that you do need to keep in mind is if you want to use all the megapixels that your camera is capable of, you should choose the ratio that corresponds to the size of your camera's image sensor. For full frame cameras, that is going to be 3:2. For a micro 4/3rds or a point-and-shoot camera, it’s going to be 4:3. If you're not sure, check your camera’s manual or the marketing materials to find out the answer. Remember that selecting a different aspect ratio than the size of your camera’s image sensor means you won't be utilizing all of those megapixels. But if you only plan to print at smaller sizes, that really doesn't matter. Using all the megapixels really only becomes important when you're going to be printing at large sizes or if you intend to crop heavily after the fact.
The decision is really a creative one, and it should come from an educated place. It's a good idea to familiarize yourself with the rough shape of each one of these aspect ratios so that you can make the right decision while you're framing your photograph. And remember if you prefer to crop to a different aspect ratio you need to keep that in mind. Make sure there is enough padding around the frame so that you can make the crop without getting rid of something that was important to the image. Keep those things in mind, and pretty soon you'll be a master of the aspect ratio.
- Use 3:2 for horizontal landscapes
- Use 4:3 for vertical landscapes
- Use the square crop for images you don't plan to print (or print them with a white boarder)
- Use 16:9 for panoramic images
- Use 5:4 and 7:6 for larger prints (8x10 and (12x14)
- When shooting for larger prints, shoot in RAW
- Consider what the image will look like when cropped
- Stick with a standard aspect ratio; choose your camera's native aspect ratio to get the most out of your sensor
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