The most important autofocus settings answer two questions: What point in the image is your camera targeting for focus? And should it constantly adjust the focus to follow a moving subject? This page introduces you to both.
Only the advanced camera modes allow you to take advantage of all the autofocus settings your camera offers: P, S, A, M resp. P, Tv, Av, M with Canon.
In the simpler full automatic or scene programmes, your camera may only allow you to influence part of it yourself or you may not be allowed to have any say at all. If you want to actively intervene in the focusing, but are not yet shooting in these advanced camera modes, it is time to switch.
There are two technically different methods, which determine where your camera can focus in the image.
Phase detection autofocus – limited to autofocus sensors | A phase autofocus can only focus in a section of the image where it has its own dedicated sensors. If you shoot with an SLR camera and look through the viewfinder, your camera will use this type of autofocus (exception: Sony's SLT models).
The number of sensors has grown over the years, starting with a few in the centre of the frame and can go up to several hundred covering a larger part of the frame.
Markings in the viewfinder will show you what area the autofocus sensors cover, they will look like in the example picture or similar.
Contrast detection autofocus – focus anywhere in the frame | Contrast detection autofocus uses data directly from the image sensor and can therefore cover the entire frame. If you see an image preview on the camera monitor or in an electronic viewfinder, your camera will use contrast detection autofocus - mirrorless cameras, SLR cameras with preview on the monitor, smartphones. (Exception: Sony's SLT models, which use a trick to divert light for separate phase autofocus even during the preview on the monitor).
Hybrid autofocus – everything is possible | Hybrid autofocus is a combination of the two methods, not a separate, technically different one.
In modern cameras, engineers have succeeded in placing sensors for phase detection autofocus on the already tiny image sensor. Then a camera can combine the advantages of both methods. How exactly depends on the manufacturer and camera model, but as a result this type of autofocus can have its sensors everywhere and focus on any point in the image.
More background knowledge can be found in How autofocus works.
Usual default: Automatic selection | The default setting for most cameras is that a a more or less clever automatic system decides which of its autofocus sensors are used, i.e. where in the frame the camera will put the focus.
In the simplest case, it hits the foreground, the spot at the closest distance. With modern technology, any number of refined procedures are possible, in particular that cameras recognise faces in real time and focus on them.
Focusing on a selected focus point | With any somewhat advanced camera you can instead focus on a selected focus point. The operation depends on the camera and the manufacturers call this setting differently: with Nikon it is called AF point control, with Canon AF method or AF area selection mode, with Sony focus area... at least that's how it is with the models I've come across. With more sophisticated cameras, buttons on the camera body help, otherwise you have to go into the menus. Some practical tips are below.
If your camera has a monitor with a touch function, it may be that a tap in the picture preview is enough to set the focus point. This is also common with smartphones.
Moving the focus point in the frame | After switching to focusing with a single focus point, your camera will display an autofocus mark in the centre of the viewfinder image or the monitor. You can also move it to another position:
Other settings for selecting the focus point | When it comes to autofocus, manufacturers are very creative, there are numerous other ways to control the position of the focus point, for example:
You can spend quite some time exploring all this. I would limit myself to automatic selection and focusing on a single metering field at first and explore the rest when you really need it for your subjects.
All cameras offer a choice of whether and how the autofocus tracks the focus:
This is called AF-S with Nikon and Sony, Canon calls it One Shot AF.
This is called AF-C with Nikon and Sony, Canon calls it Servo AF.
This is called AF-A with Nikon and Sony, Canon calls it Focus AF.
Finally, a few specific hints as to where the described autofocus settings can be found on sample camera models from Nikon, Canon, Sony. However, it is impossible to describe this for all cameras in a short text, so please consult the manual of your camera if the explanations are not sufficient for you. The same applies if your camera comes from one of the smaller manufacturers such as Fujifilm, Olympus & Co. and you do not find yourself in the examples.
On Nikon's larger system cameras (e.g. D7x00, D7x0, D8x0) there is an autofocus button to access the settings explained above, or a function button (e.g. Z6/Z7):
If your model does not have an AF button (e.g. D3x00, D5x00), there is a menu for quick settings:
With Canon I have experienced the following operation:
With Sony, the safe way to find the autofocus settings described is through the menus. The larger models have programmable C1 and/or C2 buttons that can be pre-assigned with the autofocus settings and if your model has an Fn button on the back, this will open a quick settings menu similar to the one described for Nikon.
If in doubt, go to the menus – with Sony, the labels you should look for are: