An exposure apparatus configured to project each of a plurality of radiation beams onto a respective location on a target, the plurality of radiation beams forming a desired dose pattern via a plurality of spot exposures, the nominal position of a characteristic point in the dose distribution of each of the spot exposures lying at points defining a first grid. The apparatus has, or is provided data from, a controller configured to: calculate a target intensity value for each of the plurality of radiation beams to expose the target to the desired dose pattern, the calculation using as input a rasterized representation of the desired dose pattern, the rasterized representation including a dose value defined at each of a plurality of points on a second grid, the first and second grids having the same geometry, and control the exposure apparatus to emit beams with the target intensity values.