An image processing system in which a client apparatus transmits RAW image data to a server apparatus, receives a result developed by the server apparatus, and displays onto a display area. The client apparatus reduces the RAW image data to a size suitable to display, transmits to the server apparatus, and requests development processing. At this time, the client apparatus also starts transmission processing of original RAW image data to the server apparatus. While making adjustment of the development processing to reduced RAW image data, the client apparatus and the server apparatus also execute transmission and reception processing of the original RAW image data in parallel therewith. After the development processing of the reduced RAW image data, if there is a request from the client apparatus, the server apparatus also executes the development processing of the original RAW image data in a manner similar to the reduced RAW image data.