Dual Pixel CMOS AF is an autofocus technology developed by Canon that aims to deliver the speed and responsiveness of phase detection autofocus using only the camera sensor and not a separate phase detection sensor. This has many advantages for mirrorless cameras and DSLRs being used in live view mode. Effectively, the photosites on Canon’s sensor are split into two, and the two ‘halves’ can be used to measure the distance of the subject by how much the two halves are ‘out of phase’. Other makers have their own on-sensor phase-detection autofocus systems. It erodes one of the few remaining advantages of DSLR cameras over mirrorless models.
Autofocus explained
Almost all modern cameras have an autofocus system, where the camera automatically focuses the lens on a subject in the picture. They do this with multiple focus points arranged around the frame. You can choose the focus point you want the camera to use, or you can let the camera choose the focus point automatically – it will usually choose the subject nearest the camera. Here are some more articles about autofocus, the different technologies used and how to get the best results.
STM (Canon)
STM stands for stepper motor lenses, a new type of autofocus motor used by Canon in some of its lenses. Stepper motors offer fast, precise and quiet focus adjustments, so these lenses are well suited both to regular stills photography and to video, where autofocus noise can be picked up very easily by the camera’s internal microphone. Canon’s STM lenses work very effectively with cameras using Canon’s Dual Pixel CMOS AF autofocus system.
See also: Autofocus basics
Stepping motor
As the name suggests, stepping motors move in small, incremental steps. They are simple, reliable and offer a good deal of control and precision. They’re now being used by Canon (STM lenses) and Nikon (AF-P lenses) in a number of consumer-orientated lenses, where they offer fast, quiet and smooth autofocus.
AF-P (Nikon)
This is a new autofocus technology being introduced by Nikon in its consumer-level lenses. It used different autofocus actuators to its existing AF-S (Supersonic Wave) lenses. The AF-P system uses stepper motors for a fast, quiet and smooth autofocus action that’s especially well suited to video, where you don’t want fast, sharp focus movements or audible motors that you can hear in the video.
Touch AF
Autofocus mode where you tap on a touch-sensitive screen to choose the focus point for the picture. Some cameras also offer a touch shutter option where tapping the screen not only sets the focus point but fires the shutter too.