Auto-focus
A type of camera lens that can adjust the distance of what is in focus (focal length).
Auto-focus usually provide better photo quality than fixed-focus, since auto-focus lenses can be larger and allow more light to reach the camera sensor. The downside of auto-focus is usually a delay when taking a photo (shutter lag).
Unlike fixed-focus lenses, auto-focus lenses provide "depth of field", meaning objects not at the focus distance appear out of focus (blurry).
Most auto-focus cameras mechanically change the distance between two lenses to do this using a small motor or ultrasonic actuator. Newer technologies use lenses that can change shape, providing the same functionality in a smaller package.
See: Fixed-focus
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 edges appear sharp.
More advanced auto-focus systems in phones use lasers and/or dedicated focus pixels on the main sensor. A system using focus pixels is known as phase detection (PDAF).
See: PDAF
Last updated Mar 13, 2017 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.
