Light emitting diode output power control

A method of reducing variation in optical power levels across a group of light emitting diodes includes testing each respective one of the light emitting diodes to determine an optical power level produced by that light emitting diode when connected to an electrical power source. During testing, the electrical power source delivers a substantially identical amount of electrical current to each respective one of the light emitting diodes. The optical power levels from the test all fall within a first range of values. The method includes connecting an electrical resistance in parallel with at least some of the light emitting diodes to reduce an amount of optical power produced by those light emitting diodes. After the electrical resistances are connected, all of the optical power levels produced by the light emitting diodes fall within a second range that is narrower than the first range.