A light bulb includes a base, light guide, and light source. The base is configured to mechanically mount the light bulb and receive electrical power. The light guide includes light input regions, at least one of the light input regions associated with an optical modifying characteristic, the light guide configured to propagate light by total internal reflection. The light source is located adjacent the light input regions. The light source and light input regions are variably positionable relative to one another to vary location at which light is incident on the light input regions such that light emitted from the light source is selectively apportioned between the light input regions. A characteristic of the light output from the light bulb is modified based on the optical modifying characteristic of the at least one of the light input regions and the relative positioning of the light source and light input regions.