DOUBLE TAKE

Canon’s new approach to AF on the imaging chip.

When Canon recently introduced its EOS 70D to the press, what could have been simply an update to the popular but aging 60D turned into an intriguing glimpse of new sensor technology. Due in stores in September, it may not make much difference to still photographers who use the optical viewfinder (they’ll find more to love elsewhere), but video shooters—or anyone using live view—are likely to benefit.

Besides upping the 70D’s pixel count to 20.2MP from 18MP, boosting the top ISO up a stop to 25,600, and raising the burst rate to 7 frames per second from 5.3, Canon doubled the number of photodiodes in each pixel, pairing them up in each one. This allows the camera to use phase-detection autofocus from each pixel site (though in this case phase detection covers just the center 80% of the APS-C-sized frame) during live view and video capture; on most DSLRs, this type of AF is done by diverting some of the incoming light from the lens to a second, dedicated AF sensor.

Canon also kept its traditional AF system, but picked the one from the more expensive EOS 7D—19 AF points, all cross-type, with the center one a dual-cross when used with f/2.8 or faster lenses—a vast improvement over the 60D’s 9-point system.

You’ll need this traditional AF to track fast-moving subjects. Because while the new Dual Pixel CMOS AF on the sensor seems to work well for most subjects, Canon limited the speed with which it drives the lens toward focus to gradual for video (for instance, to shift focus from one subject to another within the same shot). You won’t be able to change the speed, though a Canon rep speculated to us that focus speed control might appear in future generations of this nascent AF system.

Other improvements? The fully articulated, 3-inch, 1.04-million-dot LCD now has touchscreen controls. Built-in Wi-Fi offers the same functionality we loved in the EOS 6D. Video capture includes the full suite of H.264 recording in Canon’s flagship EOS-1D X, allows for capture at up to 1920x1080p30, and the choice of ALL-I or IPB codecs.

The EOS 70D is available for pre- sale at a street price of $1,199, body only; in a kit with Canon’s EF-S 18-55mm f/3.5-5.6 IS STM lens it goes for $1,349, and with an EF-S 18-135mm f/3.5-5.6 IS STM lens it costs $1,549.

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