Method and apparatus for forming grey-scale images on a photosensitive imaging medium, the medium being capable of spatial resolution finer than pixel dimensions of the exposing apparatus. The medium is exposed to a pixellated array of exposure sources which may be liquid crystal shutters or light emitting diodes. A transmission density is developed in imaged areas that varies non-linearly with the exposure energy received by the imaged areas in which the exposure conditions are adjusted such that the variation in average transmission over a whole pixel area from image pixel to image pixel caused by spatial energy distribution variations is less than 5% for the same energy delivered to each pixel area. The pixellated array of energy sources may be two rows of exposure pixels in a parallel but staggered configuration and associated with a SELFOC lens array, each of the exposure pixels having a light-emitting area, in which light-emitting areas of one of the two rows are substantially the same size and shape as gaps between light-emitting areas of the other of the two rows. The pixellated array may also be a single row of exposure pixels associated with an array of microlenses and the SELFOC lens array, arranged so that the expression:a/2-f tanis greater than zero, where f=focal length of a microlens, a=width of an exposure pixel, and =acceptance angle of the SELFOC lens array.