AndreTate

Agreed, and it's unfortunate that people like to legitimize the use of LEDs in halogen housings with half-baked understandings of basic optics.

​​

TxAg98

Quality, productive post. Would read again.

Flamingtaco

Length and width of the filament for/aft are critical dimensions. The thickness of the heatsink between the filaments has such a small effect on light emission as to be barely measure-able in the beam pattern. If the reflective surfaces were above and below the light source instead of to the left and right, the orientation of our bulbs would cause issues, but really they wouldn't as the bulb receptacle would be clock 90º.

Calling everyone using LED's in halogen housings is puerile, and conveniently avoids the fact that there are no laws in place declaring you can't use LED's in place of halogen bulbs. The laws only pertain to the beam pattern and intensity. Remain within the limits, don't dazzle opposing traffic, not getting flashed by other drivers ever, shouldn't matter, but some people just can't be appeased.

My son's 2010 Fusion with OEM projector housings and halogen bulbs INSTALLED AT FACTORY TEN YEARS AGO dazzle more than my LED in OEM F150 halogen housing due to having a tighter spread both horizontally and vertically. Opposing that car while cresting a hill is nasty. Some of the oem HID projectors are downright demonstrable by comparison, but in this day and age of jackwagons running off-road 60" LED lightbars on the road and I'm here trying to educate people on how they can get more light without affecting others and working with mfg's to produce bicycle lights with cutoff beam patterns, I'm the half-baked POS.

I've heard the same non-informative arguments for years that have zero basis in fact while working with an engineer that designs automotive headlight systems for a living, so you're just wasting your time.

AndreTate

Understood, thank you. So you're not the engineer who works on automotive lighting. You're just passing on second-hand information at best.

i think it would be worth your time asking him or another P.E. about SAE J3145 and it's criteria for light source equivalency, which is much more complicated than correct fore/aft position. Or you could ask him about Lumileds' patent on their fine-coil H4 bulb, which, according to Calcoast-ITL, measures at 2.3% more lumens than a standard H4 bulb, but can create increases in illumination distance of 20 to 30 meters, and perhaps he'll help explain why in ReflectorCAD, there's parameters for specifying filament offset. Maybe that'll show you the importance of not just 2D, fore-aft positioning, but also the importance of 3D, filament diameter or LED board thickness.

​​​​​​Or perhaps you can inspect this diagram from a PhD thesis. Maybe he needs to revise his thesis and delete this diagram because filament diameter, or its counterpart, board thickness, is so irrelevant as to be immeasurable. I don't know why he wasted so much space in his thesis with this diagram. Must be classic paper padding.



I appreciate your qualifications, which include installing bulbs in your son's Fusion and having a friend in the industry, and I appreciate all your input.