Surface geometry can play an important role in our ability to understand and interpret material appearance and properties. This property ranges from large-scale shape changes impacting our identification of reflections to visible surface roughness affecting how glossy a material appears. In this work we present a user study that examines numerous surface geometries that are defined at the mesoscale: small enough to be considered indicative of the material and not object geometry, but large enough to be visible from a distance with the naked eye. Subjects matched the perceived brightness of a ray-traced bumpy surface to a flat surface with adjustable intensity. Multiple classes of bumpy surface were generated and presented to subjects so that the effects of surface pattern on perceived brightness could be studied. We show that two predictive models of brightness are only conditionally accurate but that humans have a consistent means of measuring overall brightness.