Dual Pixel CMOS AF is a sensor-based, phase detection Auto Focus (AF) technology designed to provide smooth, high-performance focus tracking in movies and fast autofocus acquisition when shooting still photos in Live View mode.
It is a unique, Canon-developed technology, ideal for creating professional-looking pull-focus effects and keeping a subject moving towards the user in sharp focus while maintaining a blurred background – a defining characteristic of EOS Movies.
Thanks to this ground breaking advance, capturing a subject and retaining sharp focus, even when moving, has never been easier.
With the ability to make a subject stand out with a limited depth-of-field, comes a requirement to keep control over focus, if the main subject moves or the point of focus changes. Dual Pixel CMOS AF was developed so that control of focus during movie making is made easier and smoother – removing the perceived notions that a DSLR’s movie mode is usable only to a professional. Additionally, Dual Pixel CMOS AF was developed to enhance the usability of shooting with Live View – moving closer towards the same performance encountered when using the viewfinder.
All effective pixels on the surface of the CMOS image sensor consist of two individual photodiodes, which are read separately for phase-detection autofocus and together for imaging. Dual Pixel CMOS AF is possible over 80 percent of the height and width of the live view frame and is highly accurate without compromising on image quality.
Unlike other methods of sensor-based autofocus, which allocate either autofocus or imaging functions to specific pixels on the sensor, the pixels on a sensor featuring Dual Pixel CMOS AF can be used as imaging pixels and phase detection AF pixels. As a result, no additional imaging processing is required around pixels dedicated for AF, which ensures both quick acquisition of focus and maximum image quality during still and movie shooting.
To perform phase detection on the image plane left and right photodiodes are read independently and the resulting parallax images are used to calculate the phase-difference.
By using this phase-difference AF technique the in focus position of the lens can be calculated.
By contrast, the more conventionally used contrast AF method looks for the focal position while moving the lens back and forth, so AF speed ends up being slower and not as smooth.
With face and object tracking engaged, Movie Servo AF follows a chosen subject as it moves, or when you recompose a shot. Alternatively, just select different focus areas by simply by tapping the touch-screen when recording.
At launch, Dual Pixel CMOS AF is compatible with 103 EF lenses, spanning EF and EF-S, fixed focal length, wide-angle and telephoto lenses. The system marks a significant advancement in autofocus performance with greatly improved AF speeds.
Please view the Dual Pixel CMOS AF – EF Lens compatibility list