Aspect ratio influences how photographers frame and compose their images in a number of ways. Although it might sound confusing for beginners at first, it is a relatively simple subject to understand. In this article, we will explore aspect ratios in detail and explain everything you need to know.
What is Aspect Ratio?
In photography, aspect ratio represents the relationship between the width and the height of an image. It can be expressed as a number followed by a colon and followed by another number, such as 3:2, or by a decimal number such as 1.50 (which is simply the long side divided by the short side). Some even prefer to express aspect ratio as a decimal, followed by a colon and number 1, such as 1.50:1.
You can easily visualize any aspect ratio by allocating units to the width and the height of an image. For example, a 4:3 aspect ratio would consist of 4 equal size units for its width and 3 equal size units for its height. Similarly, an image with a 3:2 aspect ratio would be represented by 3 equal size units for its width vs 2 units for its height, as shown below:
The aspect ratio is often determined by the form factor of the camera’s film / imaging sensor, which is practically always rectangular. The most common aspect ratios of modern digital camera sensors are 3:2 and 4:3. All modern full-frame and APS-C DSLR cameras have 3:2 aspect ratio sensors, whereas 4:3 is a popular choice among smartphone, Micro Four Thirds and some medium format camera manufacturers.
As discussed further down below, some cameras allow choosing different aspect ratios through the camera menu, providing cropping options other than the native one of the image sensor.
It is important to note that aspect ratio does not represent the physical size of an image, or its dimensions in pixels – it refers only to the relationship of its width to its height. For example, the aspect ratio of 3:2 could translate to an image that is 3 meters wide and 2 meters high, as well as 3 feet wide and 2 feet high. When looking at image dimensions in pixels, a 6000×4000 image from a 24 MP camera also has the same 3:2 aspect ratio.
Lastly, when aspect ratio is expressed in two numbers separated by a colon, the first number typically refers to the horizontal side of the image, whereas the second number refers to the vertical side. For example, 3:2 indicates a horizontal image captured in landscape orientation, whereas 2:3 refers to a vertical image captured in portrait orientation. When aspect ratio is expressed in decimal numbers such as 1.50 or 1.50:1, it ignores the orientation of the image.
Why Aspect Ratio is Important
Understanding the fundamentals of aspect ratio is very important, because of the way it affects your final image. This can be especially critical at the time of physically capturing a photograph.
For example, if you capture an image with a camera in its native 4:3 aspect ratio and cram your subject or important elements of the scene to the edges of the frame, you might not be able to crop the image to wider aspect ratios. Take a look at the following image:
As you can see, the image was captured in 4:3 and I was barely able to squeeze the building, as well as the foreground structure into my framing. While it worked out at the end for this particular shot, there is simply no potential for cropping the image to fit any other aspect ratios without cutting into the building or the foreground element:
The same goes for choosing extremely wide aspect ratios, where the camera crops the top and bottom of the frame, as in the image below:
When I was using the DJI Mavic Pro drone in Cappadocia, Turkey, I forgot that I set the camera to capture images in 16:9, so I ended up with a bunch of wide images like the image you see above. Unfortunately, since the top and the bottom parts of the image were cropped out (even when shooting RAW), I will have to crop the sides of the image quite a bit to get to 3:2 or 4:3. Take a look at what changing to these aspect ratios will do the above image:
As you can see, while 3:2 might work out in the above case, 4:3 is definitely not a good option, since it is cutting into the foreground structures. If I had captured this image in its native 4:3 aspect ratio to begin with, I could have avoided this problem.
This is why paying attention to aspect ratios when composing and framing your shots is very important – always make sure to provide enough “breathing space” around your subject if your end goal is to have more cropping options later.
Native vs Choosing in Camera
As I have already mentioned earlier, the aspect ratio is often determined by the camera’s image sensor, which is its “native aspect ratio”. Some cameras, however, provide the ability to choose different aspect ratios to photographers.
For example, the Nikon Z7 allows choosing between the following:
- FX (36×24)
- DX (24×16)
- 5:4 (30×24)
- 1:1 (24×24)
- 16:9 (36×20)
Note that the first two options are both 3:2 (FX 36×24 and DX 24×16), because it is the native aspect ratio of the sensor on this camera (the second option is provided to crop the center part of the image to simulate Nikon’s APS-C / DX camera sensors). All other options, such as 5:4, 1:1 and 16:9 are not native to the camera, which means that choosing any of them will result in cropping part of the image.
While doing this reduces image resolution and file size, it is often not a good idea to switch to non-native aspect ratios. First of all, you are throwing away pixels that you will never be able to get back. So if you crop an image and decide to go back and change to a different aspect ratio, you will have to either retake the shot, or potentially lose resolution due to additional cropping that will have to take place. If you shoot in native aspect ratio, you will have the ability to change it during the post-processing step later, with minimal loss of resolution.
I can only think of two real reasons why one would want to change from the native aspect ratio. The first reason has to do with framing – if you want to prevent accidentally cutting into your subject, then switching to the aspect ratio that you will use for displaying or printing your image might be beneficial. The second reason has to do with the camera buffer and continuous shooting speed – some cameras are able to shoot longer due to storing smaller files in the camera buffer.