Patent ID: 8836843

Claim:
An image pickup apparatus arranged to detachably mount a lens unit having an optical system including a focus lens, comprising: an image pickup unit configured to accumulate charges by detecting light which passed through the optical system of the attached lens unit, and generate an image signal from the charges; a signal generation unit configured to generate a focus signal from the image signal; and a control unit configured to make a first information corresponding to an amount of movement of the focus lens on the basis of the focus signal, corresponding to the charges accumulated during a period that includes at least a predetermined period during which the focus lens is stopped, generated by the signal generation unit, transmit the first information to the lens unit, and receive information from the lens unit, wherein the control unit receives a predetermined signal for indicating whether or not the focus lens is movable by the amount of movement corresponding to the first information within a predetermined time from the lens unit, and wherein if the control unit receives the predetermined signal for indicating that the focus lens is movable by the amount of movement corresponding to the first information within the predetermined time, the control unit makes the first information on the basis of a focus signal generated from the image signal corresponding to the charges accumulated during a first period, and if the control unit receives the predetermined signal for indicating that the focus lens is not movable by the amount of movement corresponding to the first information within the predetermined time, the control unit makes the first information on the basis of a focus signal generated from the image signal corresponding to the charges accumulated during a second period after the first period.