Originally Posted by ken cummings

A clean, tight beam can be had with a PAR36 spotlight bulb that has a shielded filament. The near parabolic rear reflector sends more then half of the light in a tight forward beam. The shield in front of the filament (and inside the bulb) blocks light from spraying off into the trees. The front of the bulb needs to be clear, smooth glass, not one of the molded forms. The 4 1/2" bulb is fitted, usually, in a black rubber holder that can be clamped to your handlebars. Other cyclists could feel the infra-red in my spotlight beam from 10 feet away. There is an incredible array of different beam patterns and power levels.