Abstract: According to the focusing process of the invention, in a calibrating stage, a number of focusing positions is stored that are assigned to varying enlarging ratios. In the stage of the automatic focusing, the focusing position for an arbitrary enlarging ratio is computed by interpolation from the stored position values.The arrangement for carrying-out the process comprises memory means for the storing of the position values furnished by the position detectors for the frame holding means and the lens system support, as well as computing means for computing the focusing position for an arbitrary enlarging ratio by means of interpolation from previously stored focusing positions with respect to selected enlarging ratios.