Canons Dual Pixel CMOS Autofocus System

Dual Pixel CMOS AF is a sensor-based phase recognition autofocus (AF) technology.

It was developed by Canon and first introduced in the EOS C100 in Autumn 2012.

All effective pixels on the sensor surface of the CMOS sensor have two separate photodiodes. These are separated for phase recognition AF and read out together to generate the image data. Dual Pixel CMOS AF is available horizontally and vertically on 80% of the sensor area.

Unlike conventional sensor-based AF systems, where a specific pixel is responsible for either AF or image acquisition, the CMOS sensor pixels are responsible for both phase recognition AF and image capture. The advantage is that the AF pixels do not require any additional calculation of image data, resulting in fast focus with maximum image quality for photos and videos.

To perform such phase detection on the image sensor, the left and right photodiodes are read separately and the resulting parallax images are used to determine the phase difference. Similar to human vision, information on distance and spatiality is obtained from the parallax. This phase recognition AF technique allos the focus setting of the lens to be determined.

In contrast, the conventional contrast AF method determines sharpness by moving the lenses forwards and backwards, resulting in a lower AF speed and making the images appear less homogeneous.

At the time of introduction, the Dual Pixel CMOS AF was compatible with 103 EF and EF-S lenses - from fixed focal length to wide-angle to telephoto zoom. The newly introduced EOS R with RF lenses also offers dual pixel AF.

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