Abstract: Mechanism are provided for model-based retargeting of photolithographic layouts. An optical proximity correction is performed on a set of target patterns for a predetermined number of iterations until a counter value exceeds a maximum predetermined number of iterations in order to produce a set of optical proximity correction mask shapes. A set of lithographic contours is generated for each of the set of optical proximity correction mask shapes in response to the counter value exceeding the maximum predetermined number of iterations. A normalized image log slope (NILS) extraction is performed on the set of target shapes and use the set of lithographic contours to produce NILS values. The set of target patterns is modified based on the NILS values in response to the NILS values failing to be within a predetermined limit. The steps are repeated until the NILS values are within the predetermined limit.