Phase-detection autofocus (PDAF) for photos

What is phase-detection autofocus?

A feature that most action photographers deem indispensable, phase detection autofocus technology (PDAF) has also become a must for everyday "snappers" – but why is that?

Like any autofocus optical system, PDAF relies on sensors to determine the appropriate focus for manually or automatically selected areas. What is so ingenious about phase detection autofocus technology is that, in a swift operation, images are split into pairs upon hitting the camera. When out of focus, the light patterns of these divided images don't line up, which tells the system that the focus needs to move (and how much it needs to move) to unify the split image. The accuracy and high speed at which this process takes place is the reason why PDAF has become so valued in action photography.

Digital cameras offer different amounts of phase-detection points. These points indicate the places on which the split image can be compared. Each "point" has two sensors that are responsible for the light pattern analysis, and a higher number of points implies more focus precision.

Phase detection autofocus is a common feature for cameras today, so you won't have trouble finding options. Still, if you think this technology is crucial, don't forget to make sure that the camera you're looking for has this feature – you can easily find out with our comparisons, or by checking our category page.

As smartphone camera systems become increasingly complex and a higher number of consumers are relying solely on their phones to capture images, PDAF has become a standard feature for high-end and mid-range smartphones. Apple was one of the first manufacturers to incorporate phase detection autofocus technology on smartphones, with its iPhone 6 and iPhone 6 Plus (2014); nowadays, you'll find plenty of options in various price ranges.

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