A stepper configuration is modified by corrector plates so that an image from a reticle plane is projected to an ideal image at an object plane. The system correction is based on the premise that depth of field correction made at the reticle plane induces insignificant distortion correction. Further, distortion correction in turn induces insignificant changes in field correction. The preferred location of plates correcting for depth of field is therefore at the reticle plane, it being noted that distortion introduced by a field corrector plate at this location is negligible. Three generalized cases for correction are therefore discussed. The first case is field curvature correction where the correcting plate is registered to or close to the reticule plate; it is shown that induced distortion correction may be ignored. The second case is where field correction cannot be placed next to the reticle plate, but the field curvature induced by required distortion correction is negligible. Finally, the case is considered where field curvature induced by the correction of distortion is not negligible and must be compensated for in overall correction.