Aperture, along with shutter speed and ISO, is one of the three most important settings you control when you take a photo. It affects both the amount of light that hits your camera sensor and the depth of field of your images. Let’s look at how to pick the right aperture for a given image.

RELATED: What Is Aperture?

Wide Apertures: f/1.2-f/2.8

Any aperture wider than f/2.8 is really wide. Most fast prime lenses have an aperture of f/1.8, although some have an aperture of f/1.4 or even f/1.2. A very small handful of rare lenses have even wider apertures like f/0.95!

These wide apertures have two main uses: to let in a lot of light for night sky photography and to create a shallow depth of field for portraits.

Which use you’re going for really depends on your lens. A wide angle wide aperture lens is much more suited to astrophotography while a fast telephoto lens will take great portraits.

Mid-Wide Apertures: f/2.8-f/5.6

Apertures between f/2.8 and f/5.6 are still pretty wide. They’re the widest apertures of a lot of zoom lenses. For example, the Canon 18-55mm kit lens’s widest aperture is f/3.5 when it’s at 18mm and f/5.6 when it’s at 55mm.

The two times you’ll use an aperture in this range are when you want to use the maximum aperture of a zoom lens (either to get a shallow depth of field or shoot at night) or you’re deliberately stopping down a faster lens to get more depth of field and a slightly sharper image. Fast f/1.8 prime lenses normally take better quality images—at least from a technical standpoint—at f/2.8.

Mid Apertures: f/5.6-f/11

There’s an old photojournalist maxim: “f/8 and be there.” It means that if you set your lens to f/8, you’ll get an image that works for a newspaper in almost all situations. The depth of field is wide enough that pretty much everything in the foreground and mid-ground will be in focus, while still giving you a fast enough shutter speed that nothing gets blurry. It’s why I recommend f/8 for street photography.

The focal lengths between f/5.6 and f/11 are all in that sort of category. Unless you’re using a long telephoto lens, they’re narrow enough to give you a deep depth of field while letting you shoot your camera handheld in most lighting conditions. If you need a slightly faster shutter speed, go with something closer to f/5.6; if you want to be sure most things will be in focus, go with something nearer f/11.

If you’re not sure what aperture to use, between f/5.6 and f/8 should be your default.

Mid-Narrow Apertures: f/11-f/18

Between f/11 and f/18 you have the main narrow apertures. At this range, pretty much everything will be in sharp focus (unless you’re shooting extremely close subjects). It’s also the range where most lenses perform their best optically. They will be at their sharpest across the frame without too much vignetting, distortion, or chromatic aberration.

So, the uses for this range should be pretty clear: you use something between f/11 and f/18 when you want to maximize image quality and depth of field. They’re popular for landscape photographs. Depending on the lighting situation, you may need to use a tripod to get a good image.

Narrow Apertures: f/18-f/32

You should generally avoid using any aperture from f/18 to the minimum aperture of your lens—f/22 for most lenses, though, in the case of some zoom lenses, it can be around f/32.

The reasons are pretty simple: although the narrowest apertures give you a slightly greater depth of field than f/16, they do so at the expense of image quality throughout the image. Unless you need maximum depth of field for some reason, you’re better off just going with f/16.

You might also be tempted to go with a really narrow aperture for long exposure images, but really, you should invest in a neutral density filter. It will give you a lot more flexibility with what aperture you use and, as a result, better looking and more creative images.

Aperture controls both the depth of field and how much light hits the sensor. How much of your frame you want in focus and how fast a shutter speed you need should be your two concerns when picking an aperture.

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Harry Guinness is a photography expert and writer with nearly a decade of experience. His work has been published in newspapers like The New York Times and on a variety of other websites, from Lifehacker to Popular Science and Medium's OneZero.
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