In a control method for an image reading system comprising an image scanning apparatus selectively reading an original as a reflective or transmissive original, an image processing apparatus receiving image data read by the image scanning apparatus and executing image processing of the image data, an operating unit, and a display unit. The control method includes determining whether the original is the reflective or transmissive original, executing reading of the reflective or transmissive original based on the determination result, processing the read image data, displaying details of processing executed and the image processing, and inputting an instruction to change the details of displayed processing. When the change instruction input instructs change of a process under execution or having been already executed, the image processing is executed again from the changed process.