An apparatus (such as a keyboard) has a plurality of keycaps and a corresponding light guide film disposed on the underside of those keycaps. The light guide film has a periphery, and at least portions of that periphery are thicker than in an interior portion of the light guide film. So configured, more light can be made available for backlighting purposes in the thicker portions than at the thinner portions. These teachings include determining the various (different) thicknesses to employ for the light guide film based upon desired backlighting of one or more of the plurality of keycaps.