Autofocus

As photographers, knowing how to use our autofocus and when to use it will ensure we can capture sharp photos anywhere, during any time of day...

What is autofocus in photography?

Autofocus (AF) in photography is a setting on your camera lens that makes your camera system automatically adjust focus on a subject, making it clear and sharp.

While I’ll be referring to autofocus in the context of photography, it is just as essential in videography as it allows videographers to capture sharp footage.

What is the difference between AF and MF mode?

In photography, there are two main focus modes: autofocus (AF) and manual focus (MF).

Manual focus is used when you want to manually adjust the focus on your subject by using your lens’ focus ring.

Manual focus is often used when autofocus is struggling, such as in low light situations, when you want to shoot through an object, or when you need very precise control over your focus, like during macro work.

Autofocus is used for pretty much everything else and, in my opinion, should be the default focus mode you go to in your photos.

When should you use autofocus?

You should use autofocus for most photography scenarios, whether your subject is static or moving.

How does autofocus work?

Autofocus works by using your camera’s internal lens motors and advanced camera technology.

There are little sensors in your camera that will detect contrast or phase differences in your scene, and that is how autofocus determines how your lens should be adjusted to achieve your focus on your subject.

Now, when it comes to truly understanding how autofocus works, there are some nuances of the autofocus technology that you should know. Let’s take a look at them now.

Contrast

The first nuance is to know about the importance of contrast.

Contrast plays a crucial role in your autofocus system, especially when using a contrast-detection AF system, which I’ll cover later. You see, cameras focus by maximizing the contrast between adjacent pixels on your sensor.

If your scene has high-contrast edges, such as many areas where light and dark meet, then your camera will have an easier time focusing on them.

If you are in a scene with low contrast, such as a blank white wall, this will be challenging for your autofocus system and lead to slower or less accurate focusing.

Active vs. passive autofocus

The second nuance is to understand the difference between active and passive autofocus.

Active autofocus

An active autofocus system emits an infrared or ultrasonic signal from your camera to your subject, which bounces back to the camera. Active autofocus primarily refers to systems that actively emit a signal like your external flash.

Your camera calculates this distance to the subject based on how long it took for the signal to return. Active autofocus works particularly well in low-light environments where passive autofocus systems could struggle to find contrast in your scene.

If your camera or external flash has an active AF assist beam, which can be infrared or ultrasonic, this is what will help your camera focus in the dark. A couple of things to note about active autofocus is that it works best for subjects that aren’t too far away as well.

This is because that emitted signal needs to hit your subject and bounce back, but if your subject is too far away, it might not even hit them in the first place.

The other thing to note is to be mindful of your subject as they might absorb the signal like a furry pet or animal or if they’re too small even to reflect the signal.

If you’re curious about how to use active autofocus, it usually comes with your external flash unit. So it’s not a camera feature per se, but often a feature on your external flash unit.

To actually use active autofocus, you attach your flash to your camera, and most flash units, like my Godox TT600 speedlight, automatically enable the AF assist light.

You simply initiate autofocus by half-pressing the shutter or your back button focus button, and the AF assist light should automatically illuminate to help your camera focus. You can usually also turn it on manually if you want to pre-focus before taking a shot.

So that’s an active autofocus system; now, most cameras themselves use a passive autofocus system.

Passive autofocus

A passive autofocus system is the more common type and relies on the image data without sending any signals.

Passive autofocus systems include phase detection autofocus, contrast detection autofocus, and hybrid autofocus, which are found across all types of digital cameras, from DSLRs to mirrorless cameras to compact cameras. And this leads me to my next section.

Different autofocus systems

The third nuance is understanding the different autofocus systems. The different autofocus systems include Phase Detection AF, Contrast-Detection AF, and Hybrid AF.

To figure out which autofocus system your camera uses, you can usually do a quick search online or check your camera’s manual. But there are also some general characteristics that can help you determine which AF system you have.

Phase detection AF

Phase Detection Autofocus is commonly found in DSLRs and many high-end mirrorless cameras.

If you use a DSLR, then you almost certainly use phase detection AF through a dedicated AF sensor when you look through your optical viewfinder. Many newer, high-end mirrorless cameras also use phase detection, but directly on the image sensor.

For example, I use a Canon 6D Mark II, which is a DSLR, and it has a phase detection system.

Phase detection is known for its speed, especially when tracking moving subjects. Phase detection autofocus works by using a prism to split the light that comes into the lens into two separate images that are blurry:

When the two images don't line up with eachother, the camera knows it's not in focus and will bring the two images together to "line them up," bringing them in focus.

Contrast-detection AF

Contrast Detection Autofocus was originally found in compact digital cameras and the first generations of mirrorless cameras. Its focus technique is based on finding contrast between edges.

Contrast Detection AF excels in accuracy, particularly when shooting static scenes or where you need very fine focusing, such as in macro photography. It is known for being slower in low light and may “hunt” a bit, which is when the lens keeps moving back and forth, trying to achieve focus because it's looking for the contrast.

This is similar to when we use Manual Focus. You can have it sharp, but if you focus just a little bit too much, it can go blurry again. The same thing can happen with contrast detection autofocus, where it is blurry, then gets in focus, then can get out of focus again if there isn't much contrast:

Hybrid AF

A Hybrid Autofocus system offers a blend of the speed of phase detection and the accuracy of contrast detection. I also want to note that I’ll be discussing a hybrid autofocus mode in the later sections, but that is different from the hybrid autofocus system.

Cameras such as Canon’s EOS R Series full-frame mirrorless cameras, Sony’s Alpha series, Nikon Z series, and Fuji’s X series use Hybrid AF systems. Many manufacturers will prominently feature the Hybrid AF system as a selling point for their cameras, so if you have a Hybrid AF system, you most likely know it as it’s in cameras that are a bit more expensive.

The Hybrid AF system allows your camera to focus quickly and accurately in various lighting conditions and subjects. How it works is that it uses the speed of Phase Detection AF, and then once the images are lined up, it uses Contrast Detection AF to maximize image sharpness.

Factors that impact autofocus performance

The final nuance you should know about autofocus is the different factors that impact autofocus performance. I’ve touched on some of these already, but I wanted to cover a few others.

Lighting

The first factor that impacts autofocus performance is lighting. As mentioned earlier, lighting conditions such as low light can challenge your autofocus system and performance.

Lens speed

The second factor that impacts autofocus performance is your lens speed. Faster lenses with wider maximum aperture often focus more quickly and accurately.

For example, the Canon EF 50mm f/1.2L will have better autofocus performance than the Canon EF-S 18-55mm f/3.5-5.6 lens due to the difference in maximum apertures.

Subject contrast and color

The third factor that impacts autofocus performance is your subject’s contrast and color. If you have a subject that blends into the background or lacks any contrast, it can be difficult for your camera to focus on them.

Camera and lens compatibility

The fourth factor that impacts autofocus performance is your camera and lens combination.

Some combinations work better together, such as if you’re using a Canon lens with a Canon camera, etc. Sometimes, if you use a third-party lens, you may have a bit more trouble with autofocus.

Now that we’ve covered autofocus, how it works, and its nuances, let’s examine the different autofocus modes.

Autofocus modes

The main autofocus modes we have are Single Autofocus Mode, Continuous Autofocus Mode, and Hybrid Autofocus Mode.

Single autofocus mode

Single Autofocus Mode is meant for stationary subjects.

It’s also called One-Shot AF on Canon Cameras and AF-S on Nikon and Sony Cameras.

Being a professional portrait photographer, this is my go-to autofocus mode.

Single Autofocus Mode works by locking your focus when you press your autofocus button, whether that’s half-pressing the shutter button or your back-button focus.

Continuous autofocus mode

Continuous Autofocus Mode is meant for moving subjects.

It’s also called AI Servo on Canon Cameras and AF-C on Nikon and Sony cameras.

As a portrait photographer, I usually use this autofocus mode when I want to capture a candid pose while the subject is moving.

It works by autofocusing on your subject either by pressing the shutter button halfway down or using your back-button focus, and your camera will continuously adjust focus on your subject while they move.

Hybrid autofocus mode

Hybrid Autofocus Mode is used when you aren’t sure whether your subject will be stationary or moving.

It’s also called AI Focus on Canon Cameras and AF-A on Nikon and Sony Cameras.

As a portrait photographer, I’ll consider using this mode if I’m doing a shoot with a model that likes to flow from pose to pose and we want to capture candid shots.

One moment, they could be standing still, and the next, they move around from side to side to capture a candid image.

So those are the different autofocus modes; once you select one of those modes, you now need to be aware of what autofocus area mode you have selected.

Autofocus area modes

The autofocus area modes in photography determine how your camera uses its autofocus point to lock focus on your subject. The common autofocus area modes found on most digital cameras include Single-Point AF, Dynamic Area AF, Group Area AF, Zone AF, Auto-Area AF, and Eye/Face Detection AF.

Some of these autofocus area modes do not exist on certain camera brands. For example, Zone AF is found on most Canon cameras, while Nikon cameras have Dynamic Area AF and Group Area AF. This is just something to be aware of when you’re checking your camera, and you notice you don’t have all these autofocus area modes.

Single-point AF

The first autofocus area mode is single-point autofocus. Using this autofocus area mode, your camera focuses using one selected autofocus point.

This will give you precise control over what part of the image you want in sharp focus. Single-point AF is best for static subjects like macro, product, or portraits where you want to focus specifically on the eyes or a specific point of emphasis.

As a portrait photographer, this is my go-to autofocus area mode.

Dynamic-area AF

Next, we have dynamic area autofocus.

Using this autofocus area mode, you select a primary focus point, and your camera will use surrounding points to maintain focus on a subject if it moves from the initially selected point. Y

ou can usually adjust the number of points and use 9-points, 21-points, or 51-points.

Dynamic-area AF is best for moving subjects like an athlete or animal in wildlife where your subject might briefly move out of the single selected focus point.

Group area AF

Next is group area autofocus. Using this autofocus area mode, your focus will be achieved through a cluster of autofocus points selected by you.

You can think of this mode as a balance between single-point autofocus and the broader coverage of dynamic autofocus. Group area AF is best for subjects in groups (hence the name) and you need more focus area coverage than a single point can provide, but you still want to control the area of focus.

Zone AF

Next, we have zone autofocus. Using this autofocus area mode will be similar to group area autofocus but typically allows for a larger and more customizable zone within your frame.

It works because your camera will focus within the zone you have selected, giving priority to the subjects closest to the camera or the subject you have identified as the main subject.

Zone AF is best for a subject that is moving within a defined area.

Auto-area AF

Next up, we have auto-area autofocus. Using this autofocus area mode, your camera will automatically select the focus point or points based on where subjects are detected within your frame.

Auto-area AF is best for situations where you need to capture images quickly without time to select a focus point, such as during events or candid shots where subjects move unpredictably.

Eye/face detection AF

Lastly, we have eye/face detection autofocus.

Using this autofocus area mode, your camera will detect and focus on human eyes or faces, prioritizing them over other points.

You might have guessed it. Eye/face detection AF is best for portraits or any situation where you need to capture eyes with precise focus.

Choosing the right autofocus area mode

With so many autofocus area mode options to choose from, which one is the best? While there is no one “best” one, there is most likely the best one, given your scene’s complexity, your specific scenario, and how much control you want over your focus area.

Be sure to understand what autofocus area modes you have available on your camera, and then take note of what each one is best for. From there, experiment with the different modes. This will help you understand which mode will work best for your photography style and subject!

Autofocus scenarios

Now, to better understand when and how to use different autofocus and area modes, I want to end this guide by looking at some example scenarios and considering which mode and area mode might be best.

Portrait photography

First, let’s look at a portrait photography scenario in which you are capturing a close-up portrait, and eye sharpness is crucial. The recommended autofocus mode would be single autofocus mode.

The recommended autofocus area mode could be single-point AF or eye AF.

Single-point AF will allow you to manually place your focus point right over one of your subject’s eyes. Eye AF will allow your camera to focus on the subject’s eyes, ensuring sharpness automatically.

Sports photography

Second, let’s look at a sports photography scenario where you are photographing a fast-moving athlete.

The recommended autofocus mode will be continuous, as your subject will most likely be moving.

Depending on the camera brand you are using, the recommended autofocus area mode could be dynamic area AF or zone AF.

Dynamic-area AF and zone AF will provide a buffer if your subject momentarily moves out of your selected point.

Wildlife photography

Third, let’s look at a wildlife photography scenario in which you photograph birds in flight or moving animals.

The recommended autofocus mode will be continuous autofocus mode.

The recommended autofocus area mode could be group area AF or zone AF, depending on which camera brand you are using.

Group area AF and zone AF will provide good area coverage, allowing you to track fast and unpredictable moving wildlife.

Landscape photography

Fourth, let’s look at a landscape photography scenario where you are photographing a landscape scene where you want front-to-back sharpness.

The recommended autofocus mode will be single autofocus mode, or you may even choose manual focus.

The recommended autofocus area mode will be single-point AF.

This will allow you to focus on a specific area, typically one-third into the scene.

If you choose manual focus, you might be interested in using the hyperfocal focusing technique.

Event photography

Fifth, let’s look at an event photography scenario in which you are photographing an event and need candid shots in a dynamic scene.

The recommended autofocus mode could be continuous autofocus mode or combine the best of both worlds and use hybrid autofocus mode.

The recommended autofocus area mode could be auto-area AF or zone AF.

Auto-area AF will be great for capturing spontaneous moments and you need the quick autofocus. Zone AF is great if you want to stay in a particular spot and your subjects remain in one zone.

Macro photography

Sixth, let’s look at a macro photography scenario in which you photograph a small subject up close, like a flower petal.

The recommended autofocus mode will be single autofocus mode, or you may even choose manual focus.

The recommended autofocus area mode will be single-point AF.

This will allow you to focus specifically on one part of the flower petal.

If you choose manual focus for ultimate control, then you’d be controlling the focus ring yourself for maximum sharpness.

Street photography

Seventh, let’s look at a street photography scenario in which you photograph scenes and subjects on the street.

The recommended autofocus mode will be be continuous autofocus mode or hybrid autofocus mode.

The recommended autofocus area mode could be zone AF or auto-area AF.

Both of these would allow you to react quickly to changing scenes and allow you to concentrate on composition.

Astrophotography

Lastly, let’s look at an astrophotography scenario in which you photograph the night sky, stars, or the Milky Way.

The recommended focus mode here will be manual focus. This is because autofocus is often ineffective in the dark, and manual focus will allow you to have precise focus control on the stars or other celestial objects.

In conclusion, I hope these examples provide you with an idea of how choosing the right autofocus mode can help you achieve sharp, in-focus images across various photography situations.

I believe understanding how our autofocus works, which mode and area mode to use, when, and why is an undervalued skill when it comes to taking sharp, clean-looking images. With that being said, be sure to experiment and practice with these different autofocus modes and autofocus area modes, and you will become a master of sharp photos in no time!