Master your camera’s autofocus: which AF points to use and when to use them

Using autofocus correctly can solve a great number of the common photography problems you face on a daily basis. But easier said than done, right? Behold the bible on AF points!
In this tutorial we’ll show you everything you need to know to take control of your AF points and nail focus every time you shoot.

Focusing has never been so simple. Use any of the Basic Zone shooting modes – Full Auto, Portrait or Landscape – and your camera does all the work for you. It’s almost too easy.
A light press on the shutter button is all you need and, 99 times out of a 100, the camera will focus in a split-second and you’re ready to fire.

So why is it that many shots simply aren’t sharp in the places that matter, such as the eyes in a portrait or the rolling hills of a landscape? The answer lies in the way that the autofocus system actually works.
Left to its own devices, a typical mid-range DSLR uses all of its nine autofocus sensors, which are spread out in a wide array around the image frame.
There’s one AF point at the centre, one both above and below it, another two to the left and right, and a final pair positioned towards the extreme left and right sides of the frame.
More advanced cameras feature an additional six ‘AF Assist’ points, although these, unlike the first nine, can’t be selected manually.
Near and far
To achieve autofocus in your camera’s shooting modes your camera uses information from all nine 
AF points.
It works out the distance of each part of the scene from the camera, chooses the closest object that coincides with an AF point and locks the autofocus at that setting.
This is fine if you want to focus on the nearest object in a scene, but often that’s not the case. 
If you’re shooting a sweeping landscape, for example, you don’t want to focus on the grass in the foreground.
In these cases it’s better to select a Manual AF point. And in close-up or telephoto photography, especially with a large, wide  aperture that reduces the depth of field, pinpoint accuracy becomes even more critical.
Making the most of your range of AF points
Auto select
By default, your DSLR uses every AF point in each shooting mode but often you can choose AF points manually. Press the AF Point Selection button at the top-right of the rear of the camera (this will differ by brand and model) and the display will confirm that multi-point Auto Select AF is in use.

Manual select
To switch from AF Auto Select to Manual Select mode, press the AF Point Selection button as in the previous step, but then press the Set button. The camera will now switch from multi-point selection to using only the central AF point for autofocus. Press the Set button again to revert to multi-point Auto Select.
Change the AF point
You’re not limited to using the central AF point in Manual Select mode. After switching to single-point AF, you can use the arrow keys to switch to any of the other eight AF points. To return to the central AF point, press the Set button again.
AF modes
Manual AF point selection works in any of the various AF modes, so you can couple use of selective AF points with One Shot AF for stationary subjects, AI Focus AF for erratic subjects, or AI Servo AF for tracking moving subjects. Select the most appropriate AF mode by pressing the AF arrow key.

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