Speeding Up Your AutoFocus

How to set up advanced Canon EOS DSLR for every type of action photography.

When you need a camera that can keep pace with fast action, it’s time to consider stepping up to one of Canon’s high-end enthusiast and professional DSLRs. As you may know, these camera bodies have sophisticated autofocus (AF) systems and a greater density of AF points in the centre of the viewfinder, in addition to their faster continuous shooting speeds.

The more AF points a camera has, the more effectively it can track a moving subject across the frame using AI Servo AF. But the sensitivity and precision of the sensor at each AF point makes a big difference, too. Standard AF sensors detect focus in just one plane, either horizontally or vertically. As the name suggests, cross-type sensors can detect both horizontally and vertically, while dual cross-type sensors are even more precise as they detect diagonally as well.

The number of AF points that are available and their precision is determined by the lens attached to the camera – or more precisely, by its maximum effective aperture. For example, ‘fast’ lenses – those which have large maximum apertures of f/2.8 or greater, such as the EF 50mm f/1.4 USM or EF 85mm f/1.8 USM – open up the full potential of the 5D Mark III’s 61-point AF array. But a lens with a relatively narrow maximum aperture may allow autofocus with only 47 AF points or fewer.

via PhotoPlus – The Canon Magazine

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