PURPOSE: To transmit lens information characteristic to the photographic lens to a camera body accurately by transmitting electric signals to signal processing circuits according to resistance values of lens information resistors provided to a lens barrel side.

CONSTITUTION: When the lens barrel 2 is mounted on the camera body 1, lens information resistors 9a and 9b are connected to fixed resistors 21 and 25 respectively and the other-side terminals of the resistors 9a and 9b are grounded to the camera body 1. The resistance value of the resistor 9a regarding the F number of the this lens barrel 2 at open aperture is denoted as RL1 and the value of the resistor 9b regarding the minimum aperture value is denoted as RL2. Assuming constant currents Ia and Ib to flow from constant current sources 22 and 26 at this time, the current Ia flows through the resistor 9a and fixed resistor 21 and a constant current flows through the resistor 9b and fixed resistor 25, so signal voltages Va and Vb shown by equations are applied to signal processing circuits 24, 27. The circuits 24 and 27 reads open aperture F number information and minimum aperture value information out of the voltages Va and Vb.