1. A method of inspecting a photomask, comprising: using a simulation element to perform an initial image rendering model to determine a plurality of initial mask defects comprising defects in a photomask formed from an integrated circuit (IC) design comprising a graphical representation of an integrated circuit layout; using a simulation element to perform a plurality of modified image rendering simulations on the IC design using a plurality of modified image rendering models, that respectively emphasize different types of lithography errors relative to the initial image rendering model, to determine a plurality of sets of modified mask defects; using a comparison element to compare the plurality of initial mask defects with the plurality of sets of modified mask defects to determine falsely identified mask defects associated with the different types of lithography errors; and forming a photomask from the IC design.