A method for applying a pattern on a mask layer includes obtaining an image file representing pixels with a first pixel size in a first direction parallel to an edge of the pixel, and a second pixel size in a second direction perpendicular to the first direction, where the first and second pixel size are the same or different, treating the mask layer such that a plurality of areas with altered physical properties are created in the mask layer, the plurality of areas corresponding to a plurality of pixels of the image file, where the treatment is done such that a first and/or a second area size of an area of said plurality of areas, seen in said first and/or said second direction, is smaller than the first and/or second pixel size, respectively.