HEADLIGHTS: DESIGNER-UNITS vs UNI-SIZE UNITS

A designer-unit is a headlight unit made only for one type of car. For example, Hella part nr. 1AH 003 430-001 is the left hand headlight for an m79-m86 Saab 900 Eurofront. This light unit is used by NO other cars. All sorts of light technique types are used in designer lights, but usually not more than one (occationally two) is available for each car.

A uni-size unit is a standard sized light unit, used by thousands of different cars. They come in various shapes and sizes, also with various fittings and are also available with different types of light techniques. The most common fitting is SAE-fit. Other fitments are usually unique to one type of car.
The small round light units are 5 ¾" inches, and are usually twin mounted. The medium ones are 5", single mounted, and the large ones are 7", also single mounted. The small rectangular units are 165 x 100 mm, and twin mounted. The large rectangulares are 200x142 mm, and single mounted.

THE DIFFERENT HEADLIGHT TYPES
There are three main types of headlights, using different tecniques.

PARABOLIC REFLECTOR
The oldest type of headlight, but still very much alive and kicking. It consists of a parabolic shaped reflector to direct forwards the light emitted by the bulb, which is placed in the focal point of the reflector. The light rays then passes through the glass which has prismes moulded in, to spread the light rays latterally. One backdraft with glass, is that the thicker the glass is, the more it will reduce light output. A prisme in the glass is (relatively) thick, but necassary to spread the light in the wanted direction. Another "law of nature" is that the larger the reflector is, the more light it will provide. And vice versa. In plain english, this means: if your car has very small headlights (of parabolic reflector type), it has a very small light output.
A parabolic reflector is, as the name indicates, always round. A "rectangular" reflector is a round parabolic reflector with its top and bottom chopped off.
The benefits of the parabolic reflector light are: Proven technology, they can be made quite good (Saab, Volvo, Mercedes), and a low production cost. For the car owner, this means a smashed headlight should not cost an arm an a leg. (But they sometimes do)

DE
This means "Dreidimensionales Ellipsoidreflektor" (threedimentional elliptic reflector). In the quest for designing cars with a lower, sleeker aerodynamic front, the designers demanded smaller headlights. In the early eighties, the engineers came up with a clever computer aided design. In order to make the frontal area of the light unit smaller, without making the reflector smaller, they bent the reflector around the bulb. Wieved from the side, the reflector has an elliptic shape. Instead of using prismes to spread/direct the light rays, they wanted the light rays to have the desired direction when they left the reflector.
The parabolic reflector is a homogenous unit, but the ellipsoid-reflector is divided into several smaller light-reflecting areas. Approx. 50.000. Each small area independently directs the light rays in the desired direction. The idea of doing this was not new, but calculating the individual angle of each area required powerful computers, previously unavailable.
In front of the reflector, there is a large projector lense which collects the lightrays before they hit the road. And inbetween the lense and the reflector, there is a metal shield covering half the lense.
This shield creates a razor sharp light/darkness boarderline with absolutely no wastelight.
DE-lights were initially only dip beam or foglights, so full beam required a separate conventional parabolic reflector. (Which often suffered hugely from downsizing. See Vauxhall/Opel Calibra, Audi TT, and Mazda 323F)
Later, the DE technology was applied to full beam units. (See Ford Puma)
Strangely enough, the first company to put these newly invented mini-lights on their vehicles, was Neoplan !?! A german BUS manufactorer! …..(Then BMW caught up with them)

FF
Is short for "Free Form" reflector. Also referred to as "complex shape" reflector. As soon as the technique of letting a computer calculate the angle of each tiny reflector-area had been mastered, someone came up with the bright idea to apply this technique to the parabolic reflector. Instead of using prismes in the glass to spread the light-rays, the reflector is used to give the light-rays its desired direction. The headlight can now have a clear glass. Since a thinner glass gives more light output, this is advantageous. And the FF unit can be made in all sorts of possible and impossible shapes, which is good news for the designers. (Not that all of them cared previously, but now the light output isn't compromized) The size of the reflector area still matters, though. Small lightunit = small lightoutput. Strangely enough, Hella insists that their "3000FF" aux-driving lamp is an FF unit, but the glass is full of prismes. An FF full beam lightunit of this size with a prismed glass has no advantage over a conventional parabolic reflector unit. An FF dip beam lightunit with a prismed glass, however, has, since it uses the whole reflector. Smaller fullbeams may benefit from FF tecnology.

The HELLA BIFOCUS 5 ¾" dip beam is the predecessor of the FF tecnology. Introduced in the early eighties, the bifocus-unit represented a major improvement in dip beam technology. As we know, dip beam units only use the upper half of the reflector. If the lower half was to be illuminated, the light would be emitted upwards and blind oncoming traffic.
This is actually a big waste of perfectly good reflector area! On the bifocus, the lower half reflector is tilted down a bit, so the light emitted from here is in parallell with light from the upper half. The bulb-shield has of course a section of the bottom cut out, to allow light downwards.

The picture above does not show the full story, the illuminated area in the lower half, is larger then shown.

CIBIÈ SURFACE COMPLEXE
This well known French manufacturer also has a 5 ¾" uni-size SAE-fit version of FF available. "Available" is a relative term, because it is a well kept secret, not listed in their catalogue... Part nr. 082346

MORE FF
This technique of using (nearly) the whole reflector area at dip beam was also applied to a 7" uni-size unit and offered as an aftermarked upgrade-unit for the Mk1 and Mk2 VW Golf !? (VW Golf has non-SAE fittings)
These 7" FF-H1 dip beam units can easily be modified to fit any car with 7" uni-size units.

Hella part nr: 1B8 137 962-011 , Golf Mk1 1B8 006 210-811 , Golf Mk1, set of two. 1B8 138 310-011 , Golf Mk2 1B8 006 210-801 , Golf Mk2, set of two

Today, most cars with separate dip and full beam reflectors (often behind one common glass) use this technique on the dip beams.

Another thing concerning cars with separate dip and full beam reflectors is that when you switch to full beam, the dip beams must still be on! This is dictated by an old leftover law, dating back from the sixties. I honestly cant think of any benefits with doing so, but I'll give you several reasons why this law should be changed!
-- Leaving the dip beams on, when engaging full beam will "ruin" your night-vision. Your eyes adjust to the brighter light close to the car, and doesn't take full advantage of the full beams.
-- Your eyes will focus too close to the car, because there is so much more light close to the car than further ahead. You will then discover objects later…
-- Quite a few modern cars have very small full beam units, with a "non-spread spot" light-pattern. When you ask why, the company will explain that since the dip beams are on aswell, they will provide the "spread". Rubbish! This light-pattern is only wide close to the car, not further ahead, where it's needed! The car manufactorers only use this as an excuse to get away with mediocre full beam units, in the name of production cost! (Or styling)
-- It will put a larger load on the alternator. Instead of 2x60W, its 4x55W.
-- If you install aux driving lights, it will put an even larger load on the alternator. 6x55W. (or 4x55W+2x100W?), instead of 2x60W+2x55W (or 2x60W +2x100W?) To disable dip beams when full beams are on, see "wiring schemes".

MORE 7" FF UNITS
Another interesting lightunit to look at is the newly designed headlight for the Mercedes Geländewagen. This unit is qiute a novelty, because research and developement for the H4 7" uni-size has practically not happened since it was introduced in 1973!
ZKW of Austria designed this unit mainly to increase dip beam. It is not SAE-fit, so it will have to be modified to fit another car.

WASTELIGHT
At night, try to drive a car during heavy snowfall with full beam switched on. You cant see a sh#t! Light is emitted upwards from the headlights, and reflected by the snow directly into your eyes. Rain and fog will also reflect this light into your eyes. Even the atmosphere reflects light, but mostly blue lightrays.
Under these driving conditions you instinctly switch over to dip beam, only to discover that you're still blinded by the snow. (But not as much) A poorly designed dip beam will emit plenty of wastelight upwards.

Look closely inside a Hella or a Bosch lightunit, and you'll see there is a metal shield in front of the bulb. The shield prevents lightrays from emitting upwards, where they're not doing any good anyway. But not all lightunits have this shield. (Production cost, remember?) This is why the tip of the H4, H7, HB4 and HB1 bulbs are painted black. (With a very thick heatresistant paint) Not the perfect solution, but it helps (a bit). The Hella (or Bosch) H4 5 ¾" uni-size unit does NOT have a shield, and as I suspected, it emits plenty of wastelight. Definitely not the best lightunit to use during a snow blizzard. The Hella H1 5 ¾" dip, and the 5 ¾" bifocus uni-size units, however, both have an effective shield. Even the full beam H1 5 ¾" uni-size units from both Hella and Bosch has wastelight shields!

When it comes to emitting wastelight, a round lightunit is better than a rectangular one. (As in all other areas too) Why? The top and bottom of a rectangular reflector is not really a reflector, but a flat wall. (Floor and ceiling) A shiny flat surface under the bulb will reflect plenty of light upwards.

The non-halogen R2 bilux bulb, used by European cars up to the mid seventies, and by some Japanese cars up to the mid eighties, does not have a black coated tip. And most of the non-halogen lightunits doesn't have a wastelight shield either. When you stand in front of such an equipped car with its dip beams lit, you can actually see the dip filament. It's like staring at the sun, and then entering a dark room. Wherever you look, small lightspots dance in front of your eyes.

Incidentally, park light bulbs are a source of wastelight too. If they're integrated in the headlight (not Saab), it's easy to disarm them, when the dip beam is on. See "wiring schemes".