Each post in this series builds on information discussed in previous posts. See the Photography for Beginners page on the menu for links to all the posts.
In this post we’ll talk about focusing, primarily autofocus (AF).
It’s easy as a beginner to mostly ignore the focus aspect of photography because digital cameras handle automatic focus well. But being more thoughtful about how you focus, and where you focus, can enhance your photography. There are also situations in which you have to think about it or you’ll end up with disappointing or outright bad photos.
Pre-AF
Before we dive into the topic I want to mention a setting many cameras have that you want to make sure is turned off. It’s usually called Pre-AF (pre-autofocus) and is found buried somewhere in your camera’s menu system. You need to check the manual for your specific camera to find it.
Pre-AF might sound like a good idea, but it really only acts as a battery drain.
When Pre-AF is turned on your camera lens constantly focuses, even when you aren’t looking through the VF (viewfinder) or touching the shutter button. The idea is that this saves time because the lens will already be focused on or near your subject when you go to shoot. But the fraction of a second of time saved isn’t really worth it.
Imagine you’re at a wildlife refuge or tourist destination walking around with your camera turned on so you’re ready to take photos of everything that catches your eye. With Pre-AF activated your lens is constantly focusing even when it’s pointed at the ground or just hanging around your neck. That constant focusing is constantly draining your battery.
Sharp vs. Soft
When something in a photo is exactly in focus it is referred to as sharp. When something is just a tad out of focus it’s referred to as soft.
Soft isn’t necessarily bad. It depends on your intent.
If you try to capture a bird, but a branch in front of it is sharp and the bird is soft, you missed focus and that’s bad. If the important part of your subject is sharp and the rest is soft, but you intentionally used a shallow DOF to achieve that effect, then your photo is a success.
Autofocus Points
AF points are the points an autofocus sensor uses to detect your subject and automatically focus the camera lens on it. How many AF points you have depends on your camera model. The AF points are laid out in a diamond shape or in a grid, with one point always being in the center.
There are two types of sensing methods used in AF points, contrast and phase detect. Some cameras only use one type. Some cameras use both types, but in different AF points. Some cameras have hybrid AF points, where some or all of the points use both sensing methods.
You don’t need to know the technical details of which sensing method your camera uses. The main thing to remember is that the center AF point is almost always the most accurate. If your camera has some hybrid AF points, they are more accurate than single type AF points.
Discussion about selecting specific AF points other than the center point will be in the next post in this series.
Achieving Focus
When you half-press your shutter button you tell the camera to focus the lens. A box around the AF point(s) being used turns green to tell you the lens achieved focus. (Some camera brands use a different color, like red, but since all three brands that I’ve owned use green that’s what I’m using in this post.) If you have camera sounds turned on the camera will also usually beep to tell you it successfully achieved focused.
Sidenote: it’s best to have camera sounds turned off, unless you have a visual problem and need the audio feedback. This is especially true if you are taking pictures in crowded and/or quiet places, and it also helps conserve battery power.
Once you get a green box that’s your signal you can go ahead and press the shutter button all the way to take the picture. Wherever that green box is in the frame will be the sharply in focus part of your photo.
Autofocus isn’t 100% reliable. Sometimes you get a green box but focus was slightly off anyway. In dim light the camera may have to hunt for focus and take too long or never be able to lock on. But most of the time autofocus in modern cameras is very good to excellent.
Focusing Modes
There are three focusing modes, but if you have a budget camera it might only offer one or two. I’m using the terms I’m familiar with, but some camera manufacturers use different terminology. Whatever words are used, the concepts remain the same.
Single AF
Single Autofocus is what most photographers use most of the time. You choose an AF point for your composition that doesn’t move (often the center point, which is the default). The subject itself can be moving, such as breaking waves or a dog, but the spot within the composition frame where you focus remains the same.
Single AF is your baseline, multi-purpose focus mode.
Continuous AF
Continuous Autofocus is used for tracking a moving subject like a flying bird or a child playing tag. But in this case the AF point isn’t static, it moves around the composition frame following your subject.
Once you lock focus on your subject, as long as you keep the shutter button half-pressed the camera will attempt to keep the moving subject in focus until you snap the photo.
How well or not continuous tracking works depends on both your technique and your camera model. In some cameras Continuous AF is kinda crappy and you end up with a lot of out of focus photos. In high-end models designed specifically for sports photography it’s very good. Most cameras that offer Continuous AF fall somewhere in between.
You have a much higher chance of coming away with useable photos if you combine Continuous AF with burst mode shooting, where your camera keeps firing off rapid shots as long as you hold the shutter button down.
You’ll end up with a lot of crummy photos you have to sort through and delete doing it that way. (Sometimes hundreds, depending on what you’re shooting.) But the chance that you get several photos that are both sharply in focus and a great capture of the action is much higher than if you only take shots one at a time.
Manual Focus
In this mode the lens doesn’t autofocus, you do the focusing yourself.
How that’s accomplished depends on your camera model. Cameras that have a lens that collapses into the body use back buttons for manual focusing. ILCs (interchangeable lens cameras) and advanced bridge cameras use a focus ring on the lens barrel.
Autofocus Modes
Autofocus Modes are the different types of autofocus available when using Single AF or Continuous AF. I can’t cover all the possibilities here because different camera manufacturers can offer slightly different options, using different terminology. Higher end models usually provide more options than less expensive models.
You will need to study your camera’s manual to determine what terminology your camera’s manufacturer uses and what the different options do. Most manuals aren’t very helpful for beginners trying to understand new concepts, so it’s a good idea to search online for blogs and videos about autofocus that are dedicated to your specific camera model.
While I can’t guess which options your camera offers or what your manufacturer calls them, I can still discuss some basic concepts behind various Autofocus Modes.
AF modes are selected in the camera’s menu system.
Single Point AF
Single Point Autofocus is what it sounds like. Only a single AF point is used by the camera to achieve focus. It can be the center point or any other point on the grid that you choose.
Single Point is the most commonly used AF Mode and many people never use anything else.
Some cameras allow you to change the size of the point. Bigger is less accurate but easier to use.
Zone AF
Zone Autofocus is similar to Single Point, but instead of just using one single focus point the camera uses several points in a block. In some situations this can make it easier to lock on to your target.
If your camera offers this AF mode and you’re having trouble getting Single Point to focus quickly or you’re having a hard time tracking a moving subject, try Zone and see if it helps. Zone AF isn’t as accurate, but can come in handy in some situations.
Multiple Point AF
If your camera has a full Auto Mode it probably uses a Multi-point AF in that mode.
Similar to Zone AF, Multi-point AF uses more than one AF point to focus the lens. But unlike Zone, the AF points used can be spread around the frame, rather than in a connected block.
Think of this type of AF mode as auto autofocus. Rather than you telling the camera what to focus on by pointing a single or block of focus points at your subject, the camera evaluates the scene and chooses what it thinks is probably most important and focuses based on that evaluation.
You might see a few scattered boxes in the frame turn green. As long as your subject is covered by one of the green boxes you’re good to go and can snap the pic. If it’s not you’ll need to move you or the camera slightly and try again.
Using this AF mode usually works okay for snapshot and landscape type photos. If you’re happy with the results for the kinds of photos you take and feel it makes things easier, go ahead and use it.
But if you are using any camera mode other than Auto Mode it probably means that you decided you want more control over the photos you take, which also includes taking more control of focusing. Using a Multi-point AF mode of this type reduces your control.
Continuous Tracking Types
Some cameras offer a way to fine tune Continuous AF. My current camera offers five different types of tracking for things like a subject moving directly towards you, erratic movement, and ignoring obstacles if your subject temporarily goes behind an object.
Face and Eye Detection
Most new cameras these days offer some type of face detection. The autofocus system is programmed to recognize and focus on a human face in a composition. If there’s more than one face it tries to evaluate which one is most prominent and focuses on that. I never use it, but from what I understand it’s fairly reliable.
A more advanced form of face detection is eye detection. The AF system not only recognizes human faces, but tries to pick out the closest eye in the face and focus specifically on that, since the eye(s) being in focus is the most important thing.
It’s up to personal taste as to whether you want to turn on face detect or not. It’s handy for family photos or when shooting portraits, but it can get annoying at other times.
In a lot of cameras face detection is disabled in Continuous AF mode and can only be used in Single AF mode. Face and eye detect only work right with humans, so it’s pointless for the family pet or wildlife photography.
AF Assist Illuminator
This feature is designed to help the autofocus system in low light conditions. Your camera may or may not have this feature.
When lighting is very dim there is little contrast, and since autofocus depends on contrast to focus properly that can be a problem. If you turn AF Assist on, a beam of light is sent out from the front of the camera to illuminate the scene enough for the AF system to achieve focus.
Before using AF Assist consider the situation. If you are around other people the flash of white light from your camera may be a disturbance. If you’re trying to shoot on the downlow, the light gives you away every time. If your subject isn’t within a few feet of you, the AF assist lamp may not reach far enough to really help. The white light will ruin your night vision and that of anyone nearby if you’re shooting in the dark, and that might be important. So in many situations using manual focus instead of AF is the better choice.
I always keep AF Assist turned off and never run into situations where I need it. Either there’s enough ambient light for AF to work or I need to use manual focus anyway. Your experience may differ, and it’s up to you to whether to use it or not. There are some situations in which it may be your best option.
Since this post is already long, I had to split this topic up into two parts. The next post in this series will be a continuation where we’ll discuss ways to put the above info into use.
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