1. An image sensing system where a camera apparatus and a client device are connected for controlling the camera apparatus by the client device, comprising: image sensing means for sensing an object and obtaining an image signal thereof; detection area control means for controlling a detection area in the image signal; adjusting means for adjusting a camera parameter based on an image signal of the detection area; storage means for storing a shape and size of the detection area; display means for superimposing the detection area on an image obtained by said image sensing means after said adjusting means adjusts the camera parameter, based on the position, shape and size of the detection area; and shift instructing means for instructing said detection area control means to shift the detection area.