Auto-focus
(AF)
A type of camera system that can automatically adjust its lenses to focus on subjects at different distances from the camera.
Auto-focus generally provides better photo quality than fixed-focus, since auto-focus lenses can have a larger aperture and therefore allow more light to reach the camera sensor. Unlike fixed-focus lenses, auto-focus lenses can provide "depth of field", meaning objects not at the focus distance may appear out of focus (blurry).
See: Fixed-focus
The most basic auto-focus systems use contrast detection (CDAF), which does an electronic version of what how you would focus with your own eyes: adjusting the lens until the edges of objects appear "sharp".
More advanced auto-focus systems in phones use lasers to measure the distance from the camera to the subject, and/or dedicated focus pixels on the main sensor. A system using focus pixels is known as phase detection (PDAF).
See: PDAF
Most auto-focus cameras mechanically change the distance between two lenses to do this using a small motor or ultrasonic actuator.
Last updated Jan 28, 2022 by Rich Brome
Editor in Chief Rich became fascinated with cell phones in 1999, creating mobile web sites for phones with tiny black-and-white displays and obsessing over new phone models. Realizing a need for better info about phones, he started Phone Scoop in 2001, and has been helming the site ever since. Rich has spent two decades researching and covering every detail of the phone industry, traveling the world to tour factories, interview CEOs, and get every last spec and photo Phone Scoop readers have come to expect. As an industry veteran, Rich is a respected voice on phone technology of the past, present, and future.
