The Canon EOS Digital Rebel XSi/450D Companion

PROGRAM MODE

FOCUSING REVISITED

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situations, and to choose exposures that change the way light and dark tones are

represented in your final image.

Focusing Revisited

With your work shooting in Full Auto mode, you should now be comfortable with

the autofocus mechanism of the XSi, and pre-focusing—the process of pressing

the shutter button halfway down to autofocus—should be second nature. While

the XSi’s autofocus system is very good, no autofocus system can work perfectly

in every situation, and there will be times when you’ll need to override, or take

manual control of, the XSi’s focus. Fortunately, the camera provides a number of

autofocus control mechanisms.

Understanding Focus Points

e XSi uses a nine-point autofous system. You’ve already experienced the nine

autofocus points in the work you’ve done in Full Auto mode. So, you know that

when you half-press the shutter button to autofocus, the camera assesses your

scene and tries to determine what the subject is. It then focuses on that subject.

To let you know what it has focused on, the XSi lights up any of the autofocus

points that are on the subject it has chosen. When focusing, it’s important to

keep an eye on which points light up so that you know exactly where the camera

has focused.

However, sometimes the camera chooses the wrong subject, especially if you’re

framing a scene with different subjects at different depths