Photo- is added to nouns and adjectives in order to form other nouns and adjectives which refer or relate to photography or photographic processes, or to light.
...an eight-day ~trip to northern Greece.
...a ~sensitive detector system.
PREFIX
PHOTO-
Meaning of PHOTO- in English
Collins COBUILD. Толковый словарь английского языка для изучающих язык Коллинз COBUILD (международная база данных языков Бирмингемского университета) . 2012