The Hella FF 165mm x 100mm H4 headlamp is an OK performer. It's among the better 165mm x 100mm conversion units, and its performance is stronger than the optic-lens Hella lamp in this size format, but the Bosch unit is better, particularly in terms of beam width/evenness and control of stray light. Ditto the Cibie. It's very difficult to get good beam performance out of a reflector-type lamp of this size, because of the small active optical area. Walls, ceilings, floors, and corners take big slices out of what would otherwise be a fairly decently-sized round quasiparabolic reflector, and then you have to remember that with H4, only 55% of the total optical area is used on low beam. This Hella FF unit would be much better with a bulb shield; there's significant stray/flare light coming directly from the filament through the lens without being collected and focused by the reflector (as well as the reflections bouncing off the floor, ceiling, walls, and inner lens surface and exiting the lamp as uncontrolled streaks and spots of stray light). This lamp is DOT-certified for use on any roadgoing vehicle in North America, but it's ECE-approved (European E-code) only as a Class-A headlamp for low-speed vehicles that don't exceed 50 km/h (30 mph). Also, this headlamp is made out of thermoplastic, so the wattage limitations are much lower before you run into heat problems. The
Osram 70/65w H4 works OK in it, given adequate wiring, but I wouldn't go any higher than that.
Stern's got some beam isocandela diagrams for it on his
165mm headlight comparison page (it's listed as the "Hella DOT/ECE harmonized" headlamp). It'd be nice to see the Bosch and Cibie units plotted, too, but obtaining data like this gets expensive if you don't have your own photogoniometer. Me, I like the unit plotted at the bottom of the page! That's a projector-type H1 low beam in a 165mm x 100mm size housing. Bosch and Hella both make the same design, primarily for heavy-duty trucks and buses in Europe (Yeah...our truckers are flying blind with 1973 sealed beams, and their truckers get these units on the same trucks...life's not fair!). The projector lamp is much deeper than any of the reflector-type lights, though, so it can't easily be retrofitted to all applications that originally take a reflector type lamp.
As for the language being used to sell this FF lamp: BS, BS, BS. There's nothing 600% (or 300%, or 200%, or 100%) brighter here. The efficiency loss due to the low-beam filament cap in H4 is counterbalanced by the inefficiency of C6 (transverse) filaments and the difficulty in focusing the beam from C8 (axial unshielded) filaments in a rectangular quasiparabolic reflector like this. There's about the same amount of light overall from an H4 vs. sealed beam of this size on low beam, it's just that a good H4 light provides a wider, more useful beam distribution. And "xenon" has got to be the most hackneyed word in the whole world of automotive lighting. It's being used to sell absolutely everything — sometimes legitimately, but most of the time it's being used emptily as a hype term for blue-glass or otherwise ridiculous bulbs. Most all halogen headlamp bulbs from reputable makers contain some xenon gas as one of many ingredients in the fill gas mix, chosen to optimize the filament's light output and lifespan. This optimization varies depending on the bulb type and subtype (long life, high output, etc.)
Any opinions?
