See
here and
here . Cibies are getting the thumbs-up despite because they work better than Hellas. Get ready to plow thru some technical stuff and take a look
here. These are beam isocandela plots for Cibie and Hella 7" (large round) headlamp units. Why not photographs of the beam up against a wall? Because photographs of beam patterns are very*misleading even if the photographer has the best of intent. Pixels and film work in a fundamentally different way than human eyes, so we have to use an objective comparisons of different headlamps'*beam performance. The way to do that is with isocandela plots, which*are generated by a machine called a photogoniometer that measures the*intensity of light produced by the headlamp through a large range of*vertical and horizontal angles. The plots are just like topographical (elevation)*maps, except the squiggles and lines represent amounts of light, instead*of elevation above sea level. The beam pattern is correctly aimed as it*would be on a car on the road, and each differently-colored line*represents the threshold of a particular intensity level. Each diagram is*plotted on a chart calibrated in degrees. *Straight ahead is represented*by (0,0), that is, zero degrees up-down and zero degrees left-right.
To get a mental approximation of the units and amounts under discussion*here:
Parking lamp: About 60 to 100 candela
Front turn signal: About 500 candela
Glaring high-beam daytime running lamps (e.g. Saturn): 8000 candela * *
The parameters to pay attention to are the luminous flux (total amount of*light within the beam), the maximum intensity and its location within the*beam relative to the axial point (H,V) -- the less downward/rightward*offset, the longer the seeing distance -- stray light outside the beam pattern and effective beam width (contained within the dark-turquoise 500*candela contour)
Things to notice about these two diagrams:
(1) The Cibie produces a much wider beam pattern than the Hella. The 1000*candela line of the Cibie's beam pattern extends from 25 degrees Left to*25 degrees right, while the 1000 candela line of the Hella extends from 18*degrees Left to 20 degrees Right. At a distance of 50 feet from the car,*this means the 1000 candela-and-brighter portion of the Hella's beam is*10.5 feet narrower than that of the Cibie. The 300 cd contour of the*Cibie's pattern is *far* wider, extending from 43 degrees Left to 50 degrees Right, compared to 26 Left to 25 Right for the Hella. This means*the overall useful width of the beam pattern at 25 feet from the car, as perceived by the driver, will be 40.7 feet for the Cibie and 22.3 feet for*the Hella.
2) The total luminous flux (overall amount of light) within the beam*pattern is 695 lumens for the Cibie, 463 lumens for the Hella - the Cibie*is 50.1% more efficient. (the TLF data is listed as "Luminous Flux" in the*readings up above the isocandela diagram) *
The high beams for these two lamps (isocandela diagrams not yet scanned*in) are very similar in overall performance and amount of light -- the*critical difference is that the Cibie's high beam hot spot is located closer to (0,0) and closer to its low beam hot spot. The Hella's high beam*and low beam hot spots are separated by a fairly large vertical amount,*such that setting the lows where they belong results in most of the high*beam light going up in the trees, but pulling the high beams down so they*send light straight ahead puts the low beams 10 feet in front of the car.
Wiring size issues: Yes. You won't burn up the car if you put in H4 lights with standard-wattage bulbs, but no matter what headlamps you install (regular sealed beams or some kind of upgrade) the stock circuit starves them. Too much resistance because the circuit is made up of long lengths of thin wire; all the headlamp current goes to and through the firewall, through the ammeter, through the tiny contacts in the headlamp switch, through the tiny contacts in the high/low beam kickswitch, back through the firewall, to the front of the car for the left headlamp, and from there over to the right headlamp. Bulb output varies exponentially to the power 3.4 with voltage input; if the line voltage at the alternator is 13.5v but the headlamps are seeing only 12.0v (a common amount of voltage drop) then the headlamps are producing only 67% of the light they'd produce at 13.5v. Definitely worthwhile to install
relays.
And make sure the lamps (new or old) are
aimed correctly.
