1. In printing a document job, a method of measuring a bare surface signature of a surface within a print engine including the steps of: defining image colorant free zones on the surface, determining the location of the image colorant free zones along the surface, providing image colorant density signals along the surface, extracting the image colorant density signals of the image colorant free zones along the surface, and providing the bare belt signature of the image colorant free zones in response to the image colorant density signals of the image colorant free zones.