1. An image processing coefficient determination method of an image processing system comprising the steps of: outputting test pattern image data having a plurality of image areas each containing one or more specific pairs of amplitude/average components at at least one spatial frequency, the plurality of image areas defining a plurality of different pairs of spatial frequency amplitude/average components over the at least one spatial frequency, by an image output device for preparing an output image, measuring at least one spatial frequency characteristic of the output image, and determining spatial frequency processing coefficients from a relationship between the at least one measured spatial frequency characteristic of the output image and at least one pair of spatial frequency amplitude/average components.