The present disclosure provides a method of inspecting a photolithographic mask wherein a design database is received, and a feature of the design database is adjusted by a bias factor to produce a biased database. Image rendering is performed on the biased database to produce a biased image. A mask is also created using the design database, and the mask is imaged to produce a mask image. The biased image is compared to the mask image, and a new value for the bias factor may be determined based on the comparison.