SprachenAutofocus: Autofocus in EOS Movies
For a large part of the time, autofocus is not as useful for movie shooting as it first appears. When shooting movies, manual focus can appear more natural and is therefore easier to watch for a viewer.
All EOS cameras that feature an EOS Movie mode have had a form of autofocus that works in Movie mode, however their method of focusing meant that the autofocus is neither smooth nor natural during recording.
Hybrid CMOS AF
Hybrid CMOS AF is a focus technology found in entry-level EOS cameras and the EOS M compact system camera. Hybrid CMOS AF improves the AF performance of cameras in both Live View and EOS Movie shooting.
Hybrid CMOS AF is a combination of two previous AF technologies:
- Phase detection as used in normal AF shooting.
- Contrast detection as used in previous versions of Live View or EOS Movie focusing.
The phase detection provides speed, while the contrast detection provides accuracy.
The Canon EOS 100D DSLR saw the introduction of Hybrid CMOS AF II which provides AF across a wider area of the frame than Hybrid CMOS AF, extending out to approximately 80% of the shooting area both horizontally and vertically.
To make the system work, the phase detection pixels are embedded within the main imaging CMOS sensor. This way they can measure the subject distance from the focal plane very quickly, while the contrast AF can check for exact focus very accurately. This helps to shortcut the normal hunting in- and out-of-focus that is common with a contrast AF system by starting the search for perfect focus much closer to the final AF setting.
With the EOS 100D, Canon introduced Hybrid CMOS AF II which functions in the same way as Hybrid CMOS AF, but provides AF across a wider area of the frame, extending out to approximately 80% of the shooting area both horizontally and vertically.
Dual Pixel CMOS AF
First seen on the EOS 70D DSLR, Dual Pixel CMOS AF delivers focusing performance to a level similar to that found in more traditional video cameras, like the Canon Legria range.
The camera uses a new style of CMOS sensor where all the pixels on the sensor are used not only to form the image, but also to perform phase-difference autofocus. This is achieved by each pixel on the sensor being composed of two independent photodiodes, both of which carry out both imaging and autofocus roles.
Canon’s Dual Pixel CMOS AF technology sees all effective pixels on the surface of the sensor consisting of two individual photodiodes, which are read separately for phase-detection autofocus and together for imaging.
With this new sensor, autofocus in Live View and EOS Movie shooting feels more natural and the tracking AF performance is greatly improved in speed but and also in smoothness compared to previous systems. Compared to the Hybrid CMOS AF II, Dual Pixel CMOS AF performs around 30% faster.
In terms of coverage, the AF area available in Live View or EOS Movie shooting is equivalent to approximately 80% of the frame both horizontally and vertically, providing a wide area coverage.
The Dual Pixel CMOS AF has been designed to be compatible with a wide range of Canon EOS lenses and will work with the majority of EF lenses, including many older models that are no longer in production.
