The 3 things that will change light output and pattern are:

1) The shape of the reflector
2) The design of the lens
3) The design, characteristics, and wattage of the bulb.

The reflector does gross beam shaping, while the lens distributes the shaped beam along designed paths. The wattage of the bulb (and to a certain extent, any coatings, bulb materials, fill gases, etc.) will determine total light output, and positioning of the filament in the bulb can also influence how much light hits the various parts of the reflector and lens.

Keeping the lens and reflector constant means that the bulb is the main 'tweak' to work with. Coatings of any kind decrease light output, even though the resulting shifts in color may make them appear brighter. You can't cut a slice out of a pie and claim that you now have a bigger pie than before! (usually these bulbs have had the filament played with to put more light in the center of the beam.) Several bulbs have +30 or +50 % light outputs - redesigned and repositioned filaments to cut scatter and focus more on the 'useful' parts of the lens. Finally, You can increase the wattage of the bulb, but this adds heat to the headlights, sockets and wiring, and load on the car electrical system.

I use the Philips 'Vision Plus' plus 50 in stock wattage on my car, and get more light where I want it than with standard H4 halogens. I plan on adding heavy duty wiring and relays to the system with the stock wattage to let them draw the max possible current for which they were designed. Some kits are available that attach your headlights through relays and HD wire directly to the alternator to allow 13.6 volt operation instead of 12 volts from the battery, but this will allow flickers, surges, etc. directly at the bulbs.

__________________
John

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