A capacitance sensing apparatus includes capacitance sensor elements covered by a layer of material. The layer of material has an uneven effect on a measure of capacitance induced in the capacitance sensor elements when an object is in proximity to a sensing surface. For example, the layer of material may have a non-uniform thickness, or a property of the material may be non-uniform across the layer. The capacitance sensor elements are dimensioned to compensate for the effect.