The Big problem in front of Canon was the slow contrast based AF system in DSLRs (When used in live-view / video mode), Canon started tweaking sensor from 650D, The 650D is first Canon DSLR with distributed Phase AF pixels within the sensor, after that 700D and 100D (both) based on same technology. But the Canon 70D is a complete breakthrough, 70D have two photodiodes distributed to each microlens. As a result, two parallax images are captured at once. With Dual Pixel CMOS AF, the amount of lens drive is calculated from the amount of signal difference (amount of shift) in the AF points. When the signals of two photodiode are in agreement the Focus is achieved.
Canon’s newly-developed Dual Pixel CMOS AF, a phase-detection autofocus (AF) technology on the camera’s image sensor plane, enables users to shoot video with the new EOS 70D close to the quality of a video shot with a camcorder. Dual Pixel CMOS AF employs a revolutionary CMOS sensor on which all of the effective pixels are able to perform both still imaging and phase-detection AF simultaneously to achieve dramatically improved AF performance over other EOS cameras during Live View shooting and when shooting video.
Compared with Canon’s conventional Live View AF systems, Dual Pixel CMOS AF realizes shorter focusing times, exceptional tracking performance and smoother autofocusing during video shooting. And, because Live View shooting can be used in a manner similar to using the camera’s viewfinder, the fast and smooth AF performance allows users to concentrate more attention on the subject and composing the photo when shooting. Dual Pixel CMOS AF also supports 103 models of EF lenses (including many earlier models), enhancing a photographer’s creative options as well as maximizing the benefit of Dual Pixel CMOS AF in a variety of situations.
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