Understanding focus in photography

After discussing exposure in photography and the three settings that define it, let’s go a little further. To continue with the basics, today we’re going to talk about focus in photography. Even if you’ve never really thought about the term, you use it every time you take a picture. Focus is what happens when you press the shutter button halfway down before taking a shot. You see? It helps you control your depth of field.

In this article, I’ll explain everything you need to know about focusing: what it is for, how it works, the different types of focus, the different autofocus modes, and the “focus-and-recompose” technique.

After that, you should be much more comfortable with focusing! Well… I still get it wrong sometimes too.

Let’s start with the basics. Focusing simply means making a detail or subject appear sharp. I was not entirely accurate in the introduction when I said it happens when you press the shutter button halfway down. In reality, there are two types of focus on digital cameras: manual focus and autofocus.

The goal here is not to write a detailed article about manual focus, because frankly, there is not that much to explain. The technique is simple: you turn the focus ring on your lens while looking through the viewfinder or screen. When the scene you want to photograph looks sharp, you take the picture.

This article will focus on autofocus. As the name suggests, autofocus is the process that allows the camera to focus on a subject automatically and make it sharp. That is what I was talking about in the introduction when I mentioned pressing the shutter button halfway down.

I see two important aspects when it comes to focus:

• Knowing how to focus exactly where you want helps you get a sharp picture. That is the main purpose of autofocus: placing focus precisely where you need it.
• Knowing how to manage focus also allows you to be more creative in photography. How? Simply by deciding what you want to highlight in a photo. For example, you can deliberately focus on a specific detail of a flower, an object, or a person to make it the center of attention. The rest of the image will often become blurred.

Knowing how to use autofocus properly will help you improve the composition of your photos, by choosing the right autofocus point, mode, and so on. Let’s look at all of this in more detail.

Even if you have never heard the term before, you almost certainly know what they are. Focus points, also known as AF points or autofocus points, are at the heart of autofocus. They partly determine the quality of your focus and the possibilities you have when composing an image. These are the small red squares or rectangles you see in the viewfinder of your DSLR or mirrorless camera. A red dot lights up when focus is acquired.

I mentioned quality and possibilities because:

• The number of AF points partly determines the type of compositions you can create.
• Their quality and precision help you lock onto a subject more effectively, especially in low light or low-contrast scenes.

Without going into overly technical details, here are a few useful things to know about AF points.

This is often one of the first things you look at when buying a camera. Even though there are other important criteria, I think the number of AF points is one of the key elements to consider. Why? Because, depending on how they are spread across the frame, they determine where you can focus automatically. To put it simply: the higher you move up the camera range, the more AF points you usually get in the viewfinder.

Here are three camera examples: an entry-level body (2000D/Rebel T7), a mid-range body (800D/Rebel T7i), and a high-end APS-C body (7D Mark II). They all have a very different number of focus points.

The more AF points you have, the more creative possibilities you get in photography. On some expert cameras, you can focus near the edge of the frame, while on an entry-level camera, the focus points are fewer and often grouped near the center. If you want to focus on a subject far from the center and there is no AF point available in that area, the shot becomes much harder to take, unless you use the technique I explain later in the article.

To keep things simple, there are two main types of AF points in a viewfinder. Depending on the range of your camera, you will have more or fewer focus points, and they will be more or less precise.

• Cross-type focus points: this is the type you usually find at least in the center of the AF-point layout on DSLRs. It is generally the most accurate type of focus point because it can detect contrast in more than one direction, making it easier to focus on subjects regardless of their orientation. On low-end or entry-level cameras, you often only have one cross-type focus point, located in the center of the frame.
• Standard focus points are either vertical or horizontal. Vertical focus points work better on horizontal subjects, while horizontal focus points work better on vertical subjects.

As a small aside, on mid-range and professional cameras, you can often select a focus zone made up of several AF points, for example in the center or in the upper-right part of the frame. This allows you to tell the camera to focus on the subject within that area.

This is one of the reasons why expert and professional cameras cost more. They have many more focus points, often cross-type or higher-precision points, spread across a larger part of the frame. Some cameras now have more than 100 focus points.

This is a point you will often see in manuals or marketing material. For example, when I bought my 6D, Canon advertised a central focus point capable of focusing down to -3EV, roughly equivalent to moonlight.

Without getting too technical, keep the following points in mind:

• Cross-type and higher-precision focus points are better at detecting contrast and can therefore focus more easily on a subject. Concretely, if I try to focus with a vertical or horizontal focus point in difficult light, my camera may struggle to lock focus.
• I am often forced to use the focus-and-recompose technique, which I explain below.
• The more cross-type or high-precision focus points you have, the easier it will be to focus in difficult lighting conditions, such as late evening, a dark room, or very early sunrise.
• Ultimately, autofocus performance depends on the ambient light in the scene and on its level of contrast. For example, try focusing on a plain white wall: it is almost impossible. But if a small detail stands out from the wall, such as a dark mark, the autofocus can lock onto that detail.
• Although it is sometimes difficult to judge before buying, some cameras are known for having very powerful autofocus systems that lock onto subjects reliably. Others are a little less efficient and can struggle more.

A few brief lines on something I think is important to know when buying a lens. Every lens has a minimum focusing distance.

In the case of my Canon 70-300 L IS, the minimum focusing distance is 1.2m. What does that mean in practice? Quite simply, if you are less than 1.2m from your subject, the camera will not be able to focus on it. The autofocus will hunt back and forth and fail to lock onto anything. Try it yourself: move closer to your subject, then slowly move back. When the autofocus finally locks, you have found the minimum focusing distance.

Some lenses, such as my Canon 70-300 L IS zoom, have a relatively short focusing distance, allowing you to focus on distant details as well as close-up subjects, almost like macro photography.

This is important to know when you don’t understand why your camera cannot focus on a subject: sometimes, you are simply too close. This distance varies depending on the lens. As a general rule, the longer the focal length, especially with telephoto lenses, the longer the minimum focusing distance will be, often more than 1m. Conversely, wide-angle and ultra-wide-angle lenses usually have very short focusing distances.

There are generally three autofocus modes, two of which are really worth knowing.

• The AF-S (Nikon) / One Shot (Canon) mode: this is the camera’s default autofocus mode and also the easiest one to use. The principle is simple: you press the shutter button halfway down, the selected AF point lights up, and the camera locks focus. Once you are happy with the focused area, you can take the shot. This is the perfect mode for portraits, landscapes, and, in short, any stationary subject.

• AF-C (Nikon) / AI Servo (Canon) mode: unlike the previous mode, focus is not locked on one fixed area. This mode is mainly designed for moving subjects, whenever you need to track something in the viewfinder: birds, planes, pedestrians, cars, and so on. The camera continuously adjusts focus as the subject moves.

• Finally, the last mode, AF-A (Nikon) / AI Focus (Canon), is a mix of the two previous modes. It detects whether the subject is moving and switches to AI Servo if needed, or stays in One Shot if the subject remains still. To be honest, I never use it, and the few times I tried it, I never really managed to master it.

Be careful not to confuse these autofocus modes with your camera’s semi-automatic shooting modes.

I also wanted to clarify the different ways you can select a focus point. When you use autofocus on your camera, you generally have two options:

• Automatic selection: let’s be clear, this is the option you should avoid, even though it is often the default setting on a camera. Basically, the camera chooses which AF point or points to use. Does that sound like a good idea to you? Letting the camera decide which part of the image should be in focus? My answer: never.
• Manual selection: this is the right approach. All cameras have a button that allows you to choose the focus point, and most of the time you use the dial or directional controls on your DSLR to move to the AF point you want. This is essential if you want to choose the exact location of your focus.

I have already mentioned this technique several times throughout the article. So, what exactly does it involve? As I said, on many low-end or entry-level camera bodies, you do not have a huge number of focus points, and they are often grouped near the center of the frame. It can therefore be difficult to focus on a subject placed in a specific corner of the viewfinder while still composing the image properly.

The technique is simple: switch to One Shot / AF-S mode, choose the central AF point, which is generally the most reliable one, and focus on your subject by pressing the shutter button halfway down. You will see the focus point light up and hear a beep. Keep your finger half-pressed, then reframe your image as desired.

Obviously, the problem with this technique is that it is difficult to use with moving subjects. If you try to apply it to a moving subject, by the time you focus and recompose, the subject may already have moved, and it will end up blurred.

There is a reason why professional cameras have a large number of focus points spread across the frame. They allow you to avoid using this focus-and-recompose technique too often. Which brings us, to conclude this article on focus in photography, to the impact of autofocus on your camera gear.

I wanted to end this article with a few words on the connection between focus points and your equipment. Generally, keep the following points in mind:

• The cheapest cameras often have very few focus points. Most of the time, you will only have one central cross-type point, with standard vertical or horizontal AF points around it. In many cases, the autofocus system outside the central focus point will be relatively weak when trying to focus on elements in a scene. Even with my 6D, a camera that cost more than €1,000 and was still an entry-level full-frame DSLR, I often find it difficult to focus on certain subjects when I move away from the central focus point, which is the only really accurate one.
• As soon as you move up to a higher-end camera, the number of AF points increases. Their position is usually better too, with points spread more widely across the frame, allowing you to compose your photos more freely. You will generally also get more cross-type focus points around the center.

Here are two examples below of cameras with a large number of high-quality focus points, mostly around the center. Full-frame cameras are generally much better in this area.

• When it comes to tracking and locking onto a subject with autofocus, the higher you move up the camera range, the better the focus performance will generally be. Autofocus will be more sensitive to small details, and you will need less contrast to focus easily.
• Finally, and this is obvious, the more you move towards cameras with a larger number of higher-quality AF points, the more expensive the camera will be.

That’s it, I’m coming to the end of this article on focus in photography. You now know what you need to master it and improve your photos. If you have any questions, comments, or points that are still unclear, feel free to leave a comment at the bottom of the article. To keep learning, I invite you to discover how to take better travel photos.

I wish you beautiful photos,

Written by Sylvain PONS

I've been passionate about photography since 2010, learning as I went along. Today, I dedicate myself to guiding others in their choice of camera gear and sharing a variety of tips to improve their photography skills.

Despite our care, a mistake may have slipped into this article. If you find any, please don't hesitate to let us know so we can correct it as soon as possible and keep our information up-to-date!