I have been following this topic, just for educaional purposes and I
have a couple of thoughts.
1) Based on my research, these HID kits which allow you to retrofit a
High Intensity Discharge bulb into an existing fixture are NOT Approved
for on road use and are junk as stated by Daniel and Arif.
2) Daniel knows a lot about headlights, but isn't paying close
attention to this group, as if he did he would know that Tiger is the
single most helpful individual here to many of us, which doesn't mean
he is always right (of course).
3) Most of this discussion is worthless to most of us as it is in some
kind of headlight geek code, so as to make it impossible for laymen to
understand. Although I think the laymens description that Arif gave was
very informative for me.
4) Calling people names doesn't make you right, it only makes you look
like a jerk.
OK, maybe he's an expert on every aspect of Mercedes cars *except* the
lighting. He can take the rest of the car; I'll take the lighting.
What part of the below is in "headlight geek code"?
Halogen headlamps and HID headlamps require very different optics to
produce a safe and effective -- not to mention legal -- beam pattern. How
come? Because of the very different characteristics of the two kinds of
A halogen bulb has a cylindrical light source -- the glowing filament. The
space immediately surrounding the cylinder of light is completely dark,
and so the sharpest contrast between bright and dark is along the edges of
the cylinder of light. The ends of the filament cylinder fade from bright
An HID bulb has a crescent-shaped light source -- the arc. It's
crescent-shaped because as it passes through the space between the two
electrodes, its heat causes it to try to rise. The space immediately
surrounding the crescent of light glows in layers...the closer to the
crescent of light, the brighter the glow. The ends of the arc crescent are
the brightest points, and immediately beyond these points is completely
dark, so the sharpest contrast between bright and dark is at the ends of
the crescent of light.
When designing the optics (lens and/or reflector) for a lamp, the
characteristics of the light source are *the* driving factor around which
everything else must be engineered. If you go and change the light source,
you've done the equivalent of putting on somebody else's eyeglasses --
they may fit on your face OK, but you won't see properly.
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