A legendary and elusive creature in the world of photography, autofocus can feel almost mythical to some. For beginners—and even some intermediate photographers—its modes, functions, and best uses often remain a mystery. Look no further; let’s break it down and explore how to make the most of autofocus.
There are many things to know about photography, or at least it feels that way! Autofocus is a rabbit hole subject one can keep diving deeper into, never quite reaching the bottom. I remember when the Canon 5D III was announced, and we started getting them into customers’ hands. I received numerous complaints—not about how great and accurate it was, but about how overwhelming it seemed due to all the functions. I think people complicate it more than necessary. There were many customizations and settings. This is quickly resolved with a bit of research and understanding. No matter the camera model or brand, autofocus can still be challenging to understand but easily solved with research.
Importance of Autofocus
What are you thinking? Really? I know autofocus is essential; that's how we capture sharp photos. That is true, but sometimes, I encounter a photographer or two who believe that even if a photo is slightly out of focus, it's acceptable because everything else about the image—exposure, composition, and subject matter—is outstanding. However, I consider any image that is slightly out of focus a loss. Occasionally, you have to face the facts and move on while admitting the fault, and no matter how great a photo might appear, we must regard it as a loss due to the out-of-focus issue.
Autofocus is not created equally; different modes are used for a photographer's various situations. You have single autofocus, continuous autofocus, automatic autofocus, dynamic and zone autofocus, tracking autofocus, and face and eye autofocus. Just a few, right? All these modes were not designed to bring you pain and heartache like an old girlfriend. They were developed because each one has a specific situation where it is needed, and each can impact your photographs differently.
What Is Autofocus?
Understanding how something works is essential to grasp what it is and what it does, and autofocus is no exception. Well, how does it work? A camera autofocuses by using a dedicated sensor. This sensor measures how sharp your photo is and automatically adjusts the lens’s position to maximize its sharpness. The lens moves slightly in or out until the image's subject is in focus.
Phase Detection Versus Contrast Detection Autofocus
You may have encountered these two terms in your quest to understand autofocus, what it is, and how it works. While most mirrorless cameras use phase detection autofocus as their primary operation, we will discuss contrast detection and the hybrid system.
Phase Detection
Phase detection technology splits the light entering the camera into two beams. The camera detects the light beams for similar light patterns and then calculates how much to adjust focus to align the beams. The camera then moves the lens, creating an image in focus.
Pros of Phase Detection Autofocus
- Significantly faster than contrast detection autofocus
- More precise tracking for rapidly moving subjects
- Effective using live view (mirrorless cameras only)
Cons of Phase Detection Autofocus
- Low-light performance can struggle in darker conditions
- Live view limitations (DSLR only)
Contrast Detection
Contrast detection uses contrast between the edges of the image to find focus. It analyzes the contrast of the pixels on your camera’s sensor and moves your lens back and forth until it's in focus.
Pros of Contrast Detection Autofocus
- High accuracy for still objects
- Flexibility: Phase detection relies on dedicated focus points, while contrast detection can focus on any area in the frame
- Fine-tuned: By slightly adjusting focus back and forth, the camera can locate and pinpoint peak contrast, allowing for more precise adjustments
Cons of Contrast Detection Autofocus
- Slower in acquiring focus
- Low-contrast scenes can be challenging; the camera may struggle to achieve focus
- Focus may fail or hunt in poorly lit or low-light scenes
Hybrid Autofocus Systems
Hybrid autofocus is a system that combines both phase and contrast detection to achieve faster and more accurate autofocus by using the strengths of both systems. It combines the speed of phase detection with the accuracy of contrast detection. The phase detection sensors on the camera’s sensor will quickly calculate the distance for focus, while contrast detection fine-tunes it for accuracy. This provides excellent performance across various shooting conditions.
Types of Autofocus Modes
Single Point Autofocus (AF-S/ One-Shot AF)
Single-point autofocus is a simple and easy mode to use. This is a mode where you, the user, select a single autofocus point in a scene. This is handy when your subject is not moving; you choose one autofocus point, and the camera will focus on that area.
Single-point autofocus is commonly used in portrait, landscape, and wildlife photography, especially if your subject is obstructed by objects such as branches, a fence, or other barriers. A significant downside of using single-point autofocus is that it requires precise placement of your subject, making it less suitable for fast-moving subjects like sports or racing. Another drawback is that if the area you are trying to focus on has low contrast, the camera may “hunt” for focus and struggle to achieve it properly.
The best use for this autofocus mode is when your subject is stationary, such as landscapes or portraits, as I mentioned earlier. You can also utilize it in a controlled environment where the subject is precisely positioned and where you can manage the composition.
You can control the autofocus by using the keypad on the back of your camera to point it to the desired location in the scene you are trying to photograph.
Continuous Auto Focus (AF-C/AI Servo)
Continuous autofocus works as its name suggests. It continually tracks and adjusts the focus as the subject moves throughout the scene, refocusing as long as you have the shutter button half-pressed. This is an ideal mode for photographing wildlife, sports, or any subject in motion. It will keep the subject sharp even if they move and change distance as you compose your scene.
Automatic Autofocus (AF-A/AI Focus)
In this mode, the camera automatically switches between single-shot focus mode (for stationary subjects) and continuous focus mode (for moving subjects). You allow the camera to determine which mode to use based on your subject. This is a “general” photography autofocus mode—consider it a convenience or hybrid autofocus mode.
Pros of Automatic Autofocus
- Convenience: No need to think about which mode to use
- Great for everyday photography and snapshots
Cons of Automatic Autofocus
- Less precise compared to manually selecting a mode
- In complex scenes with multiple objects, the camera may struggle to determine the correct focus mode, leading to errors
Manual Focus
This is going to be where you manually focus the lens. I will focus on when to use manual focus, as this is where I get the most questions. The three most significant areas where I would use manual focus are macro, astro, and night photography. This is due to several reasons. The biggest is that your camera will have difficulty focusing at night due to the darkness or low-contrast areas in macro photography. I touched on those earlier as cons to phase and contrast detection. Also, the three usually require precise focus as well.
Manual focusing is typically challenging. Mirrorless cameras introduced focus peaking, a function that highlights the sharpest edges of the image with a colored overlay in live view. This allows the photographer to see what is in focus easily. This is very useful if you are adapting manual-focus lenses with adapters to your camera or for images where the focus is critical and needs to be precise, like macro photography.
Advanced Focus Modes
Zone Autofocus and Dynamic Autofocus
Zone focus is a setting that allows you to pre-focus on an area of the frame. This will be specifically helpful when you know where your subject will be within the frame. This works by you selecting the zone, and the camera chooses the autofocus points for you within that zone, with points moving around within the designated zone. You will select this mode for moving subjects like street photography, sports, pets, or kids.
Dynamic autofocus, or Dynamic-Area AF, is a focus mode that allows you to select a primary focus point. If your subject moves out of the selected autofocus point, the camera will utilize the surrounding autofocus points to maintain focus on your subject. This is ideal for tracking subjects like athletes or wildlife. Remember that this mode must be used with continuous autofocus to adjust focus as the subject moves.
Face and Eye Detection Autofocus
These are some of the most significant advancements in autofocus—one of many! The camera will automatically detect your subject's face and eyes. If you're a portrait photographer, this will immensely increase the odds that you will focus on your subject's eyes and not the eyelashes. Some cameras offer modes that you can select, such as pet detection. These modes can also be used in video.
Custom Focusing Techniques
Back Button Focus
Back-button focus is my favorite! It allows you to separate the focus from the shutter release on the camera and assign it to a dedicated autofocus button (depending on the model) or reprogram another button. There are several benefits to using back-button focus.
- Stops the camera’s autofocus from engaging each time the shutter button is depressed
- When shooting with continuous autofocus, focusing is only engaged when the dedicated button is pressed, allowing autofocus to be used only when needed. Then, you can fire the camera to take the photo with the shutter release button.
- Manual focus: The camera will only focus using the dedicated autofocus button. Most lenses allow you to use manual focus and take photos without refocusing the image with the shutter button.
One of the most significant drawbacks at first is getting used to it! You’ll want to use the shutter release button to focus and freak out when it doesn’t focus, only to realize that you set up back-button focus. It will take some coordination to get used to this!
Focus Lock and Recomposition
Nowadays, cameras have so many autofocus points that I hardly ever do this anymore. Canon’s EOS R5 can focus on roughly 5,940 areas, covering virtually the entire image! That feels a bit excessive to me! However, if your camera lacks numerous autofocus points and you need to focus on specific areas that aren't covered, you can use focus lock. AF lock is a feature that maintains the lens's focus while taking the photo. You can frame your image, set the autofocus point, focus on the desired area, hold down the AF-L (autofocus lock) button, recompose the image, and then take the shot. Problem solved; there's no need for a million and a half autofocus points!
Troubleshooting Two Common Autofocus Issues
Like anything, autofocus will occasionally have issues. Here are a few common problems and instructions for troubleshooting them.
Issue: Autofocus Hunting
Occasionally, the camera will "hunt," meaning it keeps focusing but never locks in focus. This can happen due to low light or low contrast.
Fix: Find an area in the image that is brighter and focus on that area. If the location you’re focusing on has low contrast, try to find an area of higher contrast and focus there.
Issue: Back or Front Focusing
What is this? If you focus on your subject and notice that the image is in focus more toward the front of the area you focused on, your lens is front-focusing. Conversely, if the image is more in focus toward the back of where you focused, the lens is back-focusing.
Fix: There are two ways. One is you can purchase a lens calibration tool that allows you to focus on a specific area and tells you how far the lens is front or back focusing, and you can correct it in the camera with a profile. Be aware that your camera has to be capable of doing this. Secondly, you can send your lens to the manufacturer to be recalibrated, and I suggest sending it in.
Quick Guide for Choosing the Right Focus Mode
- Portraits: AF-S + Face/Eye Detection
- Sports/Wildlife: AF-C + Zone AF/Tracking
- Landscapes: Manual Focus or AF-S
- Street Photography: AF-C or AF-S with Zone AF
- Macro: Manual Focus with Focus Peaking
In the End
While autofocus and everything that goes along with it may be confusing, a little knowledge and keeping things simple will help make this subject easier and less daunting. Take your time, study, and practice, practice, and practice! Things will become clearer and less overwhelming. Autofocus is one of the most important things you should learn initially! Most never take the time to understand it, and if they did, I guarantee they wouldn’t have missed as many shots due to using the wrong autofocus mode—I know I did early on.
