LED Bulbs?

Depends on how you define 'fundamentally wrong'. LEDs are a directional light source, whereas halogens are an omni-directional light source, they are fundamentally different. LED technology today cannot replicate a halogen filament automotive bulb, though it is continually improving. The leading design today of using opposing emitters on a thin blade means only the sides of a headlight assembly are illuminated. If you have a short highly rectangular assembly, this is less problematic than a round assembly where significant areas of the reflector will be dark, meaning areas in the beam pattern that those portions were responsible for will not receive light, which causes a non-uniform beam pattern. The more the geometry is off from center in the blade design, the more glare will likely result assuming the LED has other components of the design correct (which often they don't).

And your secondary issue observations are correct.

 

Thanks for the input! I'm an engineer by profession, but I'm not EE and don't have much experience with EM radiation (outside of what I learned in college)--this stuff is definitely interesting to me though.

By "fundamentally different" I meant that, the EM radiation coming off an LED is no different than EM radiation of the same wavelength and intensity coming from any other source.

I've read that SMD LEDs have a Lambertian distribution (which looks like it means it is proportional to the cosine of the angle to the normal of the surface of the LED, so a single SMD LED doesn't act like a point source) of emitted light. I've also seen the "blade" type orientation LED assemblies and it's easy to see why those assemblies in a reflector housing designed to work with a point source would not work well.

That being said, I would reason that, with a proper position and orientation of LEDs in an assembly, you could approximate a point source rather well (well enough for a reflector housing at least). Making that assembly for a reasonable cost and to fit the form factor of a standard halogen headlight bulb may be another question. The closest I've seen are LED assemblies that look like this one (not speaking to the quality of that specific assembly, just the orientation): https://www.amazon.com/dp/B07W7B3BKW/ref=cm_sw_r_cp_apa_fabc_7bCZFbG1SZPX9?_encoding=UTF8&psc=1

I just saw a lot of the stigma about LEDs in the stock housings and was curious what the basis was for it. I enjoy discussing stuff like this.

 

That specific design will perform poorly. While the 360 concept on the surface seems like it would work, the light must originate at the same point as a halogen filament for the geometry to be correct, meaning that design needs to be significantly smaller, otherwise you end up with bad geometry, causing lack of focus and increased glare.

If you follow the 3rd Gen headlight thread, that key distance for the H11 filament is 1.42mm.

 

I guess the question then becomes, is there a difference in the characteristics of an omnidirectional light source if we vary the radius of the "point" source? Obviously anything < the radius won't get any light and it's not a "point" if it has a radius greater than zero, but is there any difference when considering distances > than the radius of the light source?

IIRC the answer would be no (so long as the energy density at any given radius remains the same and the light is only emitted normal to the surface at every point along the surface). As long as size of the physical assembly doesn't obfuscate a significant amount of the reflected light, if you had a spherical LED assembly with some radius, r, where the LEDs could be packed tightly enough that the distance between each diode and the angles between the normal vector for each diode was sufficiently small, could you approximate a point source well enough? LEDs don't ONLY emit light normal to the surface (instead a Lambertian distribution), so the light emitted at any non-zero angle to the normal would affect how well it approximates a point source--but at when does that start to matter?

It looks like one I linked would produce something similar to a "toroid of intensity", with a cosine cross-section (in polar coords) with a minimum radius that equals the radius of the surface that the LEDs are mounted on. I assume it's not ideal, because it's a "toroid of intensity", not a uniform "sphere of intensity" that a point source would produce--it was just the "best" arrangement I had seen (with very minimal searching)--as compared to the "blade" style arrangement.

I could probably do some more digging--I imagine there are more optimal assemblies (probably non-automotive applications) compared to the cheap ones we can find on Amazon.

As I mentioned, I'm not an EE, just recalling what I learned many years ago! Input from others is always great!

 

Very interesting, but......If an LED could be properly engineered to work "perfectly" in a reflector housing, because of the significantly reduced heat output from LED's, snow & ice freeze over is still a deal breaker. That is unless a thermostatically controlled heater assembly is engineered into the housing. That would probably eliminate any benefit LED's might provide.
I've mentioned this several times. When your headlights freeze over, it's a scary experience. Light output gradually gets dimmer & dimmer until you have no usable light. LED's don't have any place being used in headlights when you live in an environment where you have snow or ice.

 

Definitely something to consider. I live in southern California, so I only ever see snow when I'm on vacation, heh.

Heat in an incandescent bulb is natural because heating the element is what produces the light (acts similar to a black body). I'm curious how cars that come with LEDs or HIDs from the factory cope with this, or rather how much heat do these types of light give off? I should probably do some Googling..

 

Yes the origin radius of the light source matters, and no your secondary statement is incorrect. That isn't how focus works and the fallacy that many LED companies producing products similar to the one you linked try to sell you on.

See this article from Philips explaining how shrinking the light source improves the focus and distance projection. Which also means that making the light source larger, reduces focus and distance projection. Article here. If you follow the 3rd Gen headlight thread, this is proven to be true. Even in the 2nd Gen headlight thread this is demonstrated to hold true.

Factory LEDs give off very little heat and will likely have icing issues in cold weather climates. This is also documented in the 3rd Gen headlight thread. Here is the FLIR reading from the thread on the factory LEDs with an ambient temp of 69 degrees.