PURPOSE: To automatically expand the blind exposure frame number range when the required number of blind exposures increases by providing a detecting means of starting the operation of a camera side film frame number counter when a film pack side film frame number counter has counted the predetermined number of frames.

CONSTITUTION: This device consists of a film frame number counter 19 and a lever 9 which are so constituted as to count the number of film frames mutually associatedly with respect to a film pack 2, wherein when said counter 19 has counted the predetermined number of film frames the detecting means constituted by the levers 9, 11, 14, 16 detects this and allows the camera side film frame number counter 5 to start operation. When the number of blind exposure frames increases because of the use of a long-sized film pack, the number of blind exposure frames which are not subjected to long-time exposure are obtained by as much as required, hence the blind exposure is accomplished rapidly.