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Understanding Focusing in Photography

Updated: Sep 16, 2022

One important technique to understand in photography, especially when you’re starting out, is the concept of focus. If you don’t focus properly, you will end up with blurry photos even when all your other camera settings are correct. Focusing can be easy or difficult depending on your subject, like a nonmoving landscape versus a fast-moving bird in flight. This guide covers everything you need to know in order to focus properly and capture sharp images.

What is Focus?

In every photo you take, there will be a plane of focus. This is the region in space with the potential to be as sharp as possible in a photo.

Some people find it useful to think of the plane of focus like a window intersecting with the scene you’re photographing. Any object in your photo that touches this window is said to be “in focus.” When you move the plane forward and backward to achieve your intended image, usually with your subject at maximum sharpness, that’s called focusing.

With modern equipment, focusing typically takes place within your lens, which has glass elements inside that can move forward and backward to change the optical path of light. Along the same lines, if you physically move your lens farther from the camera, you’ll change where the plane of focus is positioned. (This is how extension tubes work for macro photography.)

Focusing happens either automatically or manually. Automatic focus, or autofocus, is when the camera system drives a motor to move elements in your lens to change focus. To focus manually, you need to turn a ring or similar mechanism on the lens instead.

NIKON D800E + 105mm f/2.8 @ 105mm, ISO 200, 1/320, f/5.6

Manual Focus vs Autofocus

In the early days of photography, every single lens was manual focus only (and many lenses today are the same way). Autofocus is a comparatively new invention in the history of photography, first appearing on the market in 1977. Still, it’s an important one.

Autofocus systems use a motor in the camera or lens to focus on a subject you’ve selected manually or automatically. So, just press a button on your camera, and it will focus on your chosen subject – or choose one for you if you prefer. Pretty useful.

Most photographers use autofocus more often than manual focus. The main reason is simply convenience; it’s easier than focusing manually. Autofocus also tends to be faster, and, in many cases, it’s also more accurate (such as tracking focus on a moving subject). This is why sports and wildlife photographers tend to rely on autofocus so heavily.

Still, manual focus stuck around for a reason. If your camera is having trouble focusing, such as in dark conditions, manual focus lets you override any issues, or make precise adjustments that the camera may have missed. And if you set your lens to manual focus, you can lock focus for a series of photos in a row. Although most photographers use autofocus more than manual focus, it’s a good idea to be familiar with both.

Can You Autofocus with Your Camera Equipment? In order to use autofocus, at least your camera or your lens must have an autofocus motor. That seems simple enough – but “autofocus” lenses don’t always have a built-in motor, and neither does every camera on the market! Specifically, if you shoot with the Nikon D3500 or D5600 (or an older model in the same lineup), pay attention to your lens purchases. You’ll want one that is designated AF-S or AF-P if you need autofocus; avoid AF-D.

NIKON D7000 + 24mm f/1.4 @ 24mm, ISO 100, 1/2500, f/1.8

Phase Detection vs Contrast Detection

How does autofocus work at a technical level? You don’t need to know the science behind it unless you’re interested, but you still should be familiar with the two main types of autofocus systems today: phase detection and contrast detection. Each one has its own strengths and weaknesses:

  • Phase detection is very fast and good at tracking moving subjects, since it doesn’t require much computational work from your camera. However, it is also more prone to errors and internal misalignment issues. Some cameras let you calibrate your phase detection system to minimize errors. (See our detailed explanation of how phase detection autofocus works.)

  • Contrast detection requires your camera to process more data, which means it generally takes longer to lock focus. As a result, it isn’t good at tracking moving subjects. However, contrast detection does tend to be more precise, since the autofocus system is directly measuring the data from your camera sensor. This is good when your subject isn’t moving as fast, like landscape photography.

That’s all good to know, but how do you actually set one or the other for a given photo?

It’s actually quite easy. On most DSLR cameras, phase detection occurs any time you autofocus via the viewfinder. Contrast detection occurs any time you autofocus via the rear LCD screen. So, just use viewfinder or live view accordingly. (Most mirrorless cameras only have one system, usually a hybrid, so you can’t switch between them; see DSLR vs mirrorless.)