Autofocus, what is it?

The autofocus or AF, is this handy device that allows your camera to automatically make up to the mark ( map ), ie to adjust the focus depending on the distance to your subject. In order to ensure the best possible focusing, two parameters remain at the discretion of the photographer: the choice of the autofocus zone and that of the autofocus mode.

In the crosshairs

To focus, your body uses collimators (or AF points), sensors responsible for detecting your subject , generally materialized in your viewfinder or on your LCD screen by small rectangles. Each collimator corresponds to an area on which you can adjust the sharpness of your image. The more of them, the easier it will be for you to fine-tune your focus. This number varies from manufacturer to manufacturer and also depends, of course, on the range of your device. There are generally three options available to you to choose your autofocus area:

  • Single point AF zone : selection of a single point.
  • Automatic AF zone  : the device automatically “selects” the subject to focus (for a landscape photo).
  • Dynamic AF zone  : selection of a grouping of collimators, allowing to widen the map zone.

To each his own

Once your autofocus area has been chosen, it will be a question of choosing the autofocus mode best suited to your subject. There are three:

- One - time autofocus called AF-S at Nikon , Pentax , Sony and co … and One Shot at Canon : focusing is performed by pressing the shutter button halfway and remains locked as long as you hold the position. This mode is particularly recommended for still subjects.

- Continuous autofocus called AF-C at Nikon, Pentax, Sony ... and AI Servo dear Canon: the shutter button always pressed halfway, the focus is adjusted in real time, ensuring continuous monitoring of your movements. topic. It is rather suitable for sports photography

- Automatic autofocus , AF-A at Nikon, Pentax, Sony, etc. and AI Focus at Canon: this is an intermediate autofocus between point-in-time and continuous, the body automatically taking care of switching from one to the other depending on your subject's behavior. Generally little used, this mode may nevertheless have its interest for animal photography.

You will understand, which says "autofocus" does not mean that you have to let your device take care of everything. Relying entirely on technology, however high it may be, can be risky. This chance, precisely, learn to reduce it as much as possible by starting, in particular, by learning to control the autofocus of your camera. You will save time. And in photos, the time… it must not be let pass.

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