Your camera is like a faithful and efficient assistant, but it’s not the brains of the outfit. Some scenes can fool your camera into thinking that something else is the more important subject. In these situations you might debate whether to use autofocus vs manual mode, but there’s no reason you can’t still use autofocus.
Your camera’s AF system usually gets it right, but you need to know when it won’t… and what you can do about it.
Like your camera’s other automated functions, its autofocus is designed to work out what to do so that you don’t have to think about it. Most of the time it makes the right decisions and produces perfectly sharp pictures, but really it can only guess at your intentions.
If you’re in a hurry, and have no time to make manual adjustments to your camera settings, autofocus is the perfect solution.
But it’s important to know how it works and what it’s going to do, so that you can take charge of focusing in situations where the camera might make the wrong guess.
Taking control doesn’t mean you have to focus manually; Most autofocus systems are both faster and more accurate than trying to focus by eye. The trick is to set the camera up so that it does what you want in the way you expect.
The range of autofocus modes and options can look daunting, but they are quite simple when you break them down. In fact, there are just two things you need to know.
First, you need to know when the camera is going to focus. In continuous AF mode it keeps focusing all the time you keep the shutter button half-pressed.
That’s fine for action sequences, but unpredictable for regular photography – for this, you need the single-shot AF mode.
Second, you need to know what it’s going to focus on. In auto-area AF mode, the camera decides on your behalf. It’s quick and simple, but sometimes wrong. Single-point AF mode is simpler and cruder but it’s the one most experts prefer because you can make the camera focus exactly where you want.
Different DSLRs use different autofocus systems, and some look fearsomely complex, like the pro-spec 51-point system in the Nikon D300s we’re using for our outdoor photo shoot.
But the same principles apply, and in a matter of moments you can tame even this super-complex system to work simply and clearly.
Autofocus vs manual: why not focus manually?
Could you save yourself time and trouble by focusing shots like this manually? Yes and no!
The problem is that your DSLR’s optical viewfinder is not large enough or crisp enough for the pinpoint focusing that high-resolution digital sensors need if they are to deliver their full potential.
But there is a quick, simple solution: use your autofocus system to set the distance, then push the autofocus switch on the lens barrel to the M position.
The focus distance will now stay locked until you change it.
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