An image pickup system comprising an image pickup apparatus generating and outputting an image signal by receiving a light and performing photoelectric conversion, and a control apparatus sending out control parameters for performing drive control of the image pickup apparatus, the image pickup apparatus and the control apparatus being capable of communicating with each other, wherein the image pickup system comprises: a first communication section being provided in the control apparatus, capable of transmitting to and receiving data from the image pickup apparatus, transmitting multiple control parameters for controlling photographing of the image pickup apparatus to the image pickup apparatus, and receiving communicated information related to the multiple control parameters from the image pickup apparatus; a second communication section being provided in the image pickup apparatus, capable of transmitting to and receiving data from the control apparatus, receiving the multiple control parameters transmitted from the first communication section, and transmitting to the control apparatus the communicated information related to the received multiple control parameters; a first register for temporarily storing and a second register for storing the received multiple control parameters and being provided in the image pickup apparatus, wherein the multiple control parameters stored in the second register are used for photographing control; a judgment section being provided in the control apparatus and judging whether the multiple control parameters received by the second communication section are normal or not as a judgment result on the basis of the communicated information related to the multiple control parameters from the image pickup apparatus and the transmitted multiple control parameters to the image pickup apparatus; a control-apparatus-side control section being provided in the control apparatus and transmitting, when the judgment result indicates that the multiple control parameters received by the image pickup apparatus are normal, a control signal to the image pickup apparatus via the first communication section, the control signal permitting the image pickup apparatus to reflect the multiple control parameters related to the judgment result from the first register to the second register of the image pickup apparatus; and a photographing control section being provided in the image pickup apparatus and being for performing photographing control by the multiple control parameters stored in the second register. a first communication section being provided in the control apparatus, capable of transmitting to and receiving data from the image pickup apparatus, transmitting multiple control parameters for controlling photographing of the image pickup apparatus to the image pickup apparatus, and receiving communicated information related to the multiple control parameters from the image pickup apparatus; a second communication section being provided in the image pickup apparatus, capable of transmitting to and receiving data from the control apparatus, receiving the multiple control parameters transmitted from the first communication section, and transmitting to the control apparatus the communicated information related to the received multiple control parameters; a first register for temporarily storing and a second register for storing the received multiple control parameters and being provided in the image pickup apparatus, wherein the multiple control parameters stored in the second register are used for photographing control; a judgment section being provided in the control apparatus and judging whether the multiple control parameters received by the second communication section are normal or not as a judgment result on the basis of the communicated information related to the multiple control parameters from the image pickup apparatus and the transmitted multiple control parameters to the image pickup apparatus; a control-apparatus-side control section being provided in the control apparatus and transmitting, when the judgment result indicates that the multiple control parameters received by the image pickup apparatus are normal, a control signal to the image pickup apparatus via the first communication section, the control signal permitting the image pickup apparatus to reflect the multiple control parameters related to the judgment result from the first register to the second register of the image pickup apparatus; and a photographing control section being provided in the image pickup apparatus and being for performing photographing control by the multiple control parameters stored in the second register.