A method for automatically producing an optical blend mask arranged in a beam path (8) of a projector (2) in a projection system with two projectors (2), by determining an actual state of the projection system by calibrating and producing an ideal blending, ascertaining an individual distortion of the projector (2) by using a front or back projection surface (11), introduced into the beam path (8), using patterns (13) from which points are derived, ascertaining the alignment and the position of the front or back projection surface (11) within a blend mask plane, calculating the optical blending for a partial image, for positioning and/or a transformation of the ideal blending, adapting the ideal blending for compensating a soft focus, applying the ascertained, individual distortion of the projector (2) to the blending, ascertaining data of the optical blend mask and outputting data for producing the optical blend mask.