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PREFOCUSING
MASTER YOUR NIKON
In order to work efficiently, AF systems need
a reasonable amount of light; when levels
are low it can help to prefocus the lens
Prefocusing with as water), geometric patterns,
overlapping elements, and off-
centre subjects. So if you are a
landscape photographer shooting
water in misty (low contrast)
your Nikon DSLR conditions you might be in trouble
if you fail to prefocus.
How to prefocus
Separating the focusing from the review the images you are bitterly using Focus Lock
picture-taking allows you to be disappointed: the AF system Now you have seen the advantages
couldn’t keep up with the bird, and of prefocusing, it’s time to look at
ready for action in an instant your pictures are out of focus. If you how it’s done. There are a number
WORDS AND PICTURES MARK HIGGINS had prefocused, however, the AF of ways to isolate the focusing from
system would have carried out its the picture taking, but the main
refocusing, as the word job in advance, leaving you with the ones are: Focus lock, Manual
suggests, means focusing sole task of releasing the shutter at focusing, Back Button AF, and using
the lens in advance of taking the optimum moment. a computer to control the camera
Pa picture. But in this And it’s not just wildlife and sports (see box). The method you choose
instance we’re not talking about the photographers who benefit from will depend on the subject and,
quick semi-depress of the shutter- this technique; it’s also popular with ultimately, your personal
release button before you press it all landscape photographers, too. In preferences, but it’s important not
the way down, we’re talking about order to work efficiently, AF systems to confuse things by trying all the
separating the act of focusing from need contrast, detail, and a different options in one session.
the act of picture-taking, allowing reasonable amount of light. When Let’s start with a method that
you to be ready for action in an one or more of these features is most of us will be familiar with:
instant. Imagine, for instance, that lacking, the lens whirs back and Focus Lock. When we compose a
you’ve been waiting for a golden forward trying to ‘lock on’. This picture we don’t always want the
eagle to return to its nest for hours. ‘hunting’ can slow you right down, subject to be in the centre of the
As the bird approaches, you fire and stop you from taking a picture frame. In fact, sometimes we want
away hoping at least one of the altogether. AF systems also struggle the subject so far off-centre that it
shots will be sharp. But when you with highly reflective surfaces (such isn’t covered by any of the AF
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