PITCHf/x is a system developed by MLB Advanced Media under the lead of Cory Schwartz that uses three cameras to track the baseball through the strike zone. Developed in the mid-2010s, it is much more sophisticated than the earlier QuesTec system which was used to improve umpire consistency in the 2000s. In addition to providing objective judgment on whether a pitch crossed the strike zone, the system tracks data such as velocity, spin rate, and such, which is used both by teams' analytical departments and outsiders.
In 2019, Major League Baseball reached an agreement with the independent Atlantic League to use the system to call balls and strikes instead of the home plate umpire, with the latter having the ability to override the system only in very specific situations. The system had already been used in other professional leagues starting in 2015, although the Atlantic League experiment was designed to be a much more serious one, aimed at providing data that could eventually lead to its adoption throughout organized baseball. However, technical issues delayed its introduction until the second half of the season.
Similar systems already exist in other sports, such as the "eagle eye" used in professional tennis to review the referee's calls on balls close to the baselines.
- Lindsay Berra: "Game Changers: An electronic strike zone? MLB pleased with current system, keeping tabs on new technology", mlb.com, November 30, 2015.