When different types of image storage apparatus such as an image sensing apparatus and an external image processing apparatus such as a printer are connected, in order to eliminate an operation error by an operator, cumbersome operation, and so forth by enabling to automatically perform optimum direct signal processing, whether control relation between the image storage apparatus and the external image processing apparatus is a first type in which a memory in the image storage apparatus is accessed directly from the external image processing apparatus, or a second type in which processing in the external image processing apparatus can be controlled by a controller of the image storage apparatus is determined in initial communication when the image storage apparatus is connected to the external image processing apparatus, and a processing procedure for processing an image in the image storage apparatus by the external image processing apparatus is changed based on the result of the determination.