Aspect Ratio: Think of Your Crop before You Shoot

Aspect ratio is one of those photography technical terms that people often ignore, until a situation arises where it becomes critically important, and by then, it is too late. You need to think about the aspect ratio and the size of your final print before you make the shot, rather than after, to avoid disappointment.

Aspect ratio refers to the relative length and width of your image, and different cameras will have different, set aspect ratios. Many DSLR cameras have an aspect ratio of 2:3, while many point and shoot and phone cameras have an aspect ratio of 3:4.

Unsure of your aspect ratio? Look at the details for one of your photographs, and divide the length (in pixels) of the shorter side by the longer side. An answer of 0.67 is 2:3, and 0.75 is 3:4. For example, with my Canon T1i, the final photographs are 4752 pixels by 3168 pixels. 3168 divided by 4752 is 0.67 or 2:3.

Aspect Ratio: So What?

Aspect ratio matters when you decide to print your photographs. In the United States, there are a variety of standard print sizes (4x6, 5x7, 8x10 and so forth), and each of these has a different aspect ratio. Depending on what size of print you choose, you may need to crop, which results in a loss of some of the original image. The infographic, above, provides a visual look at what kind of cropping to expect, based on your original aspect ratio and chosen print size.

If you are more of a numbers person, then you can think of it this way:

• With an aspect ratio of 2:3, there will be no loss as a 4x6. There will be a loss of 7% of the width for a 5x7, 17% for an 8x10, and 36% for widescreen.
• With an aspect ratio of 3:4, there will be a loss of 11% of the height for a 4x6, 5% of the height for a 5x7, 6% of the width for an 8x10, and 43% of the width for widescreen.

The 'so what' part of aspect ratio is that you need to worry about it, particularly if your subject fills the frame or is close to one or more of the edges. Of course, you can choose where to crop (rather than equally from both sides, as shown), but you may be out of luck trying to print a tall image as widescreen or a wide image as an 8x10 or 16x20 canvas.

This is easier to understand with visual examples. The infographic, above provides two scenarios for photographs and how each crop would affect them. Aspect ratio most often becomes an issue when a critical part of your subject is located near the edge (or edges) of your photograph. Printing on canvas further exacerbates this problem, as canvas-wrapped prints involve using a portion of the edge of the image to 'wrap' around the inch or more thick sides of the canvas.

Lower Falls of the Yellowstone River, original aspect ratio, 2:3

The photograph of the double rainbow at the Lower Falls of the Yellowstone River, above, was one that I was considering printing as a 16x20 inch wrapped canvas print. It was shot with my DSLR camera at an aspect ratio of 2:3, which means that I would have to crop off 17% of the height in order to fit it onto a 16x20 inch print. An example of what that crop might have looked like is below.

Lower Falls of the Yellowstone, showing the loss (gray) in cropping to a 16x20 aspect ratio.

You can already see the problem. The top of the falls is getting slightly chopped off on the left edge, while the end of the rainbox (and most of the double rainbow) are getting chopped off on the right edge. I cannot keep both elements and would have to choose which to lose more of.

But wait. Then there is also the canvas wrap. I have to also factor in at least an inch around all the sides of the cropped image that will be wrapped around the edge of the frame. This further cuts in to the final, displayed image, as seen below. The double rainbow is gone completely, the edge of the falls wraps around the canvas, and the edges of the main rainbow fall around the wrapped edge too.

In the end, I had to go with another image entirely. Since I had composed this original image so close in to the falls and the rainbow, I was unable to salvage the picture for printing as an 16x20 wrapped canvas.

Plan for Cropping – Keep Your Aspect Ratio in Mind 

The most important part of aspect ratio is simply to know what it is and how it can affect your final print. If you are doing a family shoot for someone who wants a big canvas print hanging above their fireplace, then you will want to be sure to shoot a little 'wide' to accommodate all the family members in the final print – without anyone losing the top of their head or the bottom of their leg! (Read more about important topics to consider when printing photographs in this article on Photography Gifts for the Holiday.)

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Zooming vs. Cropping: perspective in photography

One of the most basic decisions when taking a photograph is what to include within the frame, and countless books, articles, and blog posts have been written about composition within that frame. But one often overlooked aspect of this discussion is the difference between zooming and cropping when getting to the final composition.

A wide shot in the process of being cropped down to a closer-in shot.

Zooming, of course, is changing the length of your lens to create the final composition (whether on a point-and-shoot, DSLR, or any camera in-between). Zooming happens in the field, while you are taking a photograph. Cropping, on the other hand, is changing the photograph itself, after it has been taken, by selecting a smaller section of the original photograph to make the final image. Zooming happens with your lens or with your feet; cropping happens on your computer.

The distinction matters for several reasons. One is that cropping decreases the amount of pixels in your final image, which can impact how well you can blow up and display or print the final image. The second is that how you choose your zoom (based on where you stand) impacts the perspective of the final photograph, while cropping does not. Wide angle lenses (or wide focal lengths) tend to expand and distort perspective, while zoom lenses (and narrower focal lengths) tend to compress a scene and make objects seem relatively closer together. These different focal lengths can greatly change the perspective of your scene.

Why does changing perspective matter? Let me illustrate with an example.

I recently retired my car. After fifteen years and nearly 150,000 miles, it was time to start seriously considering a different car before the next winter set in. Decisions were made, and the weekend came to say goodbye to my old car. As a goodbye, I decided to take it for a last spin and photo shoot down by the lake.

I wanted to take a 'car portrait' with the lake and trees as the backdrop, so I decided to take a series of shots at different zoom lengths to see which one offered the best perspective. To accomplish this, I had to zoom with my lens as well as my feet. For the first image, at 18 mm (the widest focal length for the lens I was using), I was standing very close to the car, slightly in the road itself. For the 35 mm shot, I had to back up to just across the road. This gave me the same compositional placement as the first shot (with the car the same approximate size within the frame). Then I repeated the process of backing up and taking another picture at 50, 100, 150, 200, and 270 mm (the maximum zoom amount for the lens I was using).

Impact of changing focal length (and backing up) on perspective.

This collage shows six of those images, each shot at the same ISO (100) and aperture (f/16). The top row of shots was shot at a shutter speed of 1/100th of a second, and the bottom row of shots was shot at 1/60th of a second (to make the darker tree backdrop a little lighter). The differences between each of the shots are purely a result of the changing perspective from each of the different focal lengths.

Comparison of 18 mm and 35 mm focal lengths on perspective

The differences are quite apparent when comparing the widest shot, 18 mm, with the next widest shot, 35 mm. The 35 mm length is considered to be most similar to the view and perspective that is captured by our eyes, and this photograph matches how the car 'naturally' looked to me at the time. The wider 18 mm view creates distortion in closer objects, which exaggerates the lines of the front of the car in particular. This view of cars is often used to make them seem large, grand, or imposing, as the car seems to dominate over the wide views in the background.

This distortion of objects at wide focal lengths can create problems when photographing portraits. While a distorted look is common in photographs of cars, a wide angle and up-close photograph of a person is far less flattering and tends to over-emphasize features, making noses look large or faces look wide. This is why lens in the 85-120 mm lengths are often referred to as 'portrait' lenses: these focal lengths give a perspective of the human face that is considered more flattering.

But back to the discussion of cropping. While I can crop an image I took from farther away to make it look like I was standing closer to that object or using a longer zoom, cropping cannot replicate the changes in perspective from actually standing closer to that object.

Same image file, as originally shot (left) and cropped down (right)

The photograph on the left was taken with the 18 mm focal length while I was standing at the same location as the 270 mm version with the car in the same relative position in the frame as in the series above. The photograph on the right was cropped from the photograph on the left to create the same relative position and size of the car in the frame.

Comparison of 270 mm shot (left) and 18 mm shot from same location, cropped (right)

This image compares the zoomed in shot at 270 mm (on the left) with the shot cropped in version from the 18 mm to imitate the composition of the 270 mm shot (on the right). The loss of pixels and therefore clarity and detail is evident between the two. The 270 mm shot is 4752 x 3168 pixels, while the cropped version is only 357 x 238 pixels. You should also notice that the perspective between the two shots is unchanged. Cropping in a shot does not change the perspective of the shot. Only zooming in or out for the shot and moving your feet changes the perspective.

Comparison of 35 mm and 270 mm focal lengths on perspective

Standing in one location (such as where I took the 270 mm shot) and changing the zoom on your lens will make photographs that are different. It will not, however, make photographs that have any differences in perspective. The relative locations and impact of the foreground and the background will remain the same. If you want to change the perspective, if you want to emphasize one object over another or influence their relationships to each other, you will need to change your zoom and move your feet.

Moving your feet can impact your photography in many ways. Read up on aperture and how moving your feet can improve your shots here: Remember the Background and Move your Feet.