dry firing a camera; clicking the shutter without film
Refers to pressing the shutter button when there is no film loaded, or to advance the film without taking a picture. A technical term from the film camera era.
I dry fire the camera to advance the film.
I accidentally dry fired and missed an important moment.
Compound of 空 (kara, 'empty') and 写し (utsushi, 'copying' or 'photographing'), literally 'empty photographing'.