Shooting optical system

A camera optical system for performing flange back adjustment by moving a lens unit included in the camera optical system in an optical axis direction, the camera optical system comprising:

• a drive gear engaging a lens holding frame for holding the lens unit;
• a drive unit for rotating the drive gear;
• a first gear not interlocked with the rotation of the drive gear driven by the drive unit;
• an operation unit for the flange back adjustment, for rotating the first gear;
• a detection unit for detecting a relative positional relationship between the first gear and the drive gear;
• and
• a control unit for driving the drive unit so as to rotate the drive gear based on the positional relationship detected by the detection unit, thereby moving the lens holding frame in the optical axis direction so that the flange back adjustment is performing and then moving the lens to a position where the flange back adjustment was performed.