A method of adjusting a read-out condition and/or an image processing condition for a radiation image comprises the steps of carrying out preliminary read out prior to carrying out final read out for obtaining an image signal which represents a radiation image stored on a stimulable phosphor sheet and which is to be used for reproducing a visible radiation image, and creating a histogram of a preliminary read-out image signal obtained by the preliminary read out. An image information range, which is necessary for reproducing the visible radiation image, is determined from the histogram. A read-out condition and/or an image processing condition is adjusted in accordance with a latitude of the image information range so that a latitude of the reproduced visible image is changed so as to widen nonlinearly when the latitude of the image information range widens.