How to start controlling the autofocus

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:

• If the camera has a touch display (and you have turned it on if necessary), you just have to tap on the desired position in the picture.
  
• Otherwise you can move the marker with the direction keys on the back of the camera. With Canon, you have to press a button   beforehand.

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:

• The size of the individual measuring field can be selected to be different sizes.
• Subject tracking: You select a point to focus on in the frame and the camera keeps it there, even if your subject moves or you pan the camera.
• A subject detection system recognises faces and automatically focuses on the eyes. This function also already exists for animals and especially birds.

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:

• One-shot focus when the shutter button is pressed; if successful, the autofocus stops and does not change focus again.

This is called AF-S with Nikon and Sony, Canon calls it One Shot AF.

• Continuous tracking of focus as long as you keep the shutter button lightly pressed; the autofocus will try to follow a moving subject.

This is called AF-C with Nikon and Sony, Canon calls it Servo AF.

• There is also automatic switching between these two modes. Then, at the moment of focusing, the camera will decide whether it detects movement and choose one of the two modes.

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):

• Automatic or manual selection of the focus point: AF/Fn button together with the front command dial.
• For manual selection of a focus point: arrow keys on the back move the marker; the Z models also have a small knob for this, more conveniently accessible with the thumb.
• Focus tracking: AF button together with the rear command dial.

If your model does not have an AF button (e.g. D3x00, D5x00), there is a menu for quick settings:

• Press the i button to open the menu and again to change settings
• Automatic or manual selection of the focus point: select AF area mode with the direction keys, press OK.
• For manual selection of an AF point: arrow keys on the back move the highlighting
• Focus tracking: Select the focus mode entry with the arrow keys, press OK.

With Canon I have experienced the following operation:

• Automatic or manual focus point selection: find the  button on the body.... When pressed, you can change the AF point selection. If the button does not exist, your model has an entry in the Quick Settings menu, which you can access by pressing the - button.
• When selecting an AF point manually: You must first tell the camera that you want to move the focus point with the  button. Then you can move it with the arrow keys or – if available – tap on the touch screen.

• Focus tracking: This does not seem to be consistent... On SLR cameras I have seen an AF button on the body, labelled DRIVE AF, but also other controls. Please ask your camera's manual... Canon calls this choice "AF mode" and talks about
  
• One-Shot AF for single shot
• Servo AF for tracking autofocus.
• Alternatively, you can find everything in the camera menus.

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.