If a camera zooms in on something that is being filmed or photographed, it gives a close-up picture of it.
...a tracking system which can follow a burglar round a building and ~ on his face...
PHRASAL VERB: V P on n
ZOOM IN
Meaning of ZOOM IN in English
Collins COBUILD. Толковый словарь английского языка для изучающих язык Коллинз COBUILD (международная база данных языков Бирмингемского университета) . 2012