Aspect ratio: what it is and why it matters

Did you go to see Wes Anderson's glorious fondant fancy of film The Grand Budapest Hotel? Did you notice how the size of the picture varied depended on the era being portrayed in the story? As the story moved between 1985, 1968, and 1932, the aspect ratio, or size of the image, jumped from 1.85:1 to 2.35:1 to 'Academy Ratio'. This was part of Anderson's story-telling technique: the aspect ratio provided viewers with a visual cue for each period of the narrative. It's also a reflection of the changes to aspect ratio that film and television have experienced over the years. But what about photographers? Where does aspect ratio come into stills?

Frame size

Maybe we need to back-track and establish precisely what we mean by 'aspect ratio' first. It's the size of the image expressed as a ratio, width to height. You'll often see film-making aspect ratios expressed as a value to 1 (like to 2.35:1 and 1.85:1 mentioned earlier), whereas the most common photography aspect ratios are 3:2, 4:3, and 1:1, although there are plenty more besides. If your image has an aspect ratio of 3:2, it will be three units wide and two high. When you come to print it, you might choose a 6×4" or a 12×8" print.

Originally, these aspect ratios were as a result of our film sizes. Lots of medium format cameras produced square, or 1:1, images; 35mm cameras used film that measured 36 by 24 millimetres, giving an aspect ratio of 3:2. What's referred to in the film-making world as 'Academy Ratio' is very close to 4:3. It's also the common aspect ratio you'll find in smartphone cameras as well as Micro Four Thirds and some medium format cameras. 16:9 is usual for recording video.

While our digital sensors might preserve these aspect ratios in their physical dimensions, at the press of a button I can switch between 3:2, 4:3, 16:9, and 1:1 on my camera. And when I import an image into Lightroom or edit it in Snapseed, I can select from 1:1, 3:2, 4:3, 5:4, 7:5, 8.5:11, 16:9, or settle upon an entirely idiosyncratic free-styled aspect ratio. But why would I want to?

Composing the frame

It's about composition, and dividing and filling your frame.

Photographers talk a lot about subject placement, about the different rules that can be used to divide the frame, and about negative space. All of these elements contribute to creating visually appealing, dynamic images that draw the eye. It follows, then, that the dimensions of the frame will have an impact on composition: on where you place your subject and how much space surrounds it and how you divide your frame.

Different rectangles

We've already written about the square crop here on Photocritic, and how the eye has a tendency to move around a square frame, as opposed to across it, which it does with a rectangular crop. When changing between 3:2 and 4:3 crops, are there any considerations that need to be made?

At its simplest, you have more space to fill with a 3:2 frame. Depending on your style and your subject, this can mean your subject has more room to breathe compared to a 4:3 crop. But it can also mean your subject has that bit too much space and feels a touch lost. You certainly need to be aware of this when you're shooting; and indeed if you intend to have prints made.

When I photographed my cousin on his graduation day, I adhered to my preferred 3:2 aspect ratio. It was how I approached filling the frame on the day and, consequently, how I processed the images afterwards. However, when my aunt had her prints made, she opted for a 24×18 canvas. I had to re-crop her favourite shot in a hurry. You can see both of them here. Can you see why I prefer the 3:2 aspect ratio in this instance? It doesn't feel nearly as squashed as the 4:3 version does.

If you compare these sunset photos, you can see how much of the view the 4:3 version loses when compared with the 3:2 aspect ratio. It can prove difficult to fill the extra space in a landscape shot, but sometimes you need it, too.

Of course, you don't have to adhere to 3:2 or 4:3 aspect ratios. I decided that 4:5 worked best for this bee enjoying the Sicilian springtime flowers. The more compact frame focused attention on the bee better than the larger 2:3 version.

Don't forget, if you switch from landscape to portrait orientation, then the aspect ratio will alter format accordingly. Width always goes first, thus 3:2 will change to 2:3 and 4:3 becomes 3:4. Or in the case of the bee, it's 4:5.

Opting for a different aspect ratio doesn't necessarily mean that you need to use a different compositional rule; however, in some circumstances, you might find the Golden Ratio preferable to the rule of thirds. It depends on your vision for the image. But do think about how much space you need around your subject. If you're struggling to fill it, think of trying 4:3; if it looks squashed, consider 3:2. Or try something else. Try not to feel too constrained by the constraints of aspect ratio.

But I will leave you with closing thoughts from xkcd. Who could put it better?

What is the rule of thirds?

This week's Photography Fundamentals column digs into composition, and one of the most-cited 'rules' of the discipline: the rule of thirds. Even if you don't know what it is, you've probably heard of it. We are, therefore, here to explain what it is and why it's useful. And then when you understand the rule and you know how to implement it, you can go ahead and break it properly. We have a natural tendency to place our subjects in the centre of the frame. It makes sense, logically, to have our point of focus right in the middle, being gloried by its surroundings and utterly unavoidable to the eye. Except that centred subjects don’t really make for very interesting images. There’s an unmistakable flat and dull quality to them. Compare this:

With this:

Next time you’re watching a film or TV, notice where the heads and the eyes of the people doing the talking are. I’ll bet they’re not in the centre of the frame.

Instead, they’ll be positioned slightly to one side. They’ll probably be making use of what’s called the rule of thirds.

Imagine that your frame is divided by four lines: two running horizontally and two vertically. They are equally spaced and split the frame into nine smaller rectangles. The points at which the four lines intersect create four ‘points of interest’. This grid is your guide for composing an image.

Aim to position subjects that run upright through your image along one of the vertical tri-lines. Lines running across the image—especially skylines and horizons—should run along a horizontal tri-line. (Definitely not through the centre with a horizon.)

Aim to place anything that’s of particular significance to the composition, for example the eyes in a portrait and the sun in a sunset scene, on one of the points of interest.

Variations

I often find that rather than using the rule of thirds to place my subjects, I have a natural predeliction for the Golden Rectangle. It's based on the mathematical princple of the Golden Ratio: an irrational number equal to approximately 1.618. It's also known as Phi (φ). If you want the technical explanation, it's

If you divide a line unevenly into two sections a (longer) and b (shorter), the ratio of these two sections will equal φ if a divided by b is equal to the sum of a plus b divided by a.

Yes. Ahem.

Rather than divide your frame using three equally spaced lines along each edge, as you would with the rule of thirds, you have two longer sections (a) either side of a shorter section (b). The ratio of the longer side to the shorter is the golden ratio.

It looks like this:

Square crops

If you're using a square crop for any of your photos, you might find that the rule of thirds doesn't produce the sort of dynamic image that you're used to with a rectangular frame. That's because the eye tends to move around a square photo, rather than across it. For this reason, centred subjects often work effectively in square frames. Or try dividing the frame into triangles, and using those for balance.

TL;DR

• The rule of thirds is a compositional aid that places two equally spaced lines across your frame, and two down it
• The horizontal lines can be used for the strong placement of horizons and skylines
• The vertical lines can be used to position key vertical elements in your frame
• The four points at which the lines intersect are known as 'points of interest'
• Use the points of interest to place significant elements of your composition, for example the eyes in portraits or the sun in sunsets, in your frame
• There are variations on the rule of thirds, based on the mathematical principle φ
• The rule of thirds doesn't necessarily work with a square crop; you might find a centred subject works better

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