Video: How phase detection autofocus works
(Digital Photography Review)

Have you ever wondered how your DSLR`s autofocus works? Wonder no more! YouTuber ZY Productions has created a succinct video that details how phase detection autofocus (PDAF) systems work inside DSLR cameras. As noted in the video, phase detection autofocus applies specifically to DSLRs, since it relies on a dedicated autofocus sensor and a translucent section of a DSLR`s mirror to achieve focus - components you won`t find inside a mirrorless camera. The exact type of autofocus system depends entirely on what camera you have. Newer DSLRs have robust autofocus systems, with more image coverage and more cross-type focus points - the importance of which is documented in the video - while older cameras might not have as much coverage or as many cross-type focus points (if any at all). Regardless of what DSLR you use and how capable its autofocus system is, knowing how your camera`s autofocus works and what its shortcomings are should help you to overcome any issues and limitations you come across. If you`d like a more robust explanation, Photography Life has a great article explaining the process in more detail.