From the worlds leading authority on automotive lighting......
http://www.danielsternlighting.com/about/about.html
http://dsl.torque.net/images/DSL_8885.pdf
High
Intensity
Danger
One type of improper light source bears special mention
because of its extreme capacity to be severely detrimental to
safety. “HID retrofit kits” are being widely marketed through
readily-accessible retail and mail-order channels. These socalled
“retrofits” consist of a D2R or D2S arc capsule (2800
or 3200 lumens, and one source is marketing “upgrade”
capsules of approximately 4600 lumens) and associated
electronic control equipment, with an adaptor by means of
which the capsule can be inserted into a headlamp designed
to accept a tungsten-halogen bulb. The massive degree by
which such sources exceed the luminous intensity of the
halogen bulbs correct for the headlamp creates tremendous
glare. The light-producing arc within the D2R or D2S capsule
is of a different size, shape and placement and, in the case
of transverse-filament bulbs, orientation within the capsule
than the light-producing filament within a halogen bulb.
The edges and endpoints of the light source are also of very
different demarcation characteristics (sharp for a filament,
fuzzy for an arc). This is why gas discharge headlamps require
different optics than tungsten-halogen headlamps. When a
gas discharge source is placed into a headlamp designed
to accept a tungsten-halogen bulb, extreme beam pattern
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Low Beam Headlamps
Where Does the Glare Come From?
damage occurs. The effects on seeing light are highly variable,
but the effect upon glare is always severe and detrimental,
i.e., vastly increased glare. There are also electric-shock
hazards associated with the use of gas discharge equipment,
which operates at high voltage, in headlamp systems not
incorporating proper shielding or weatherproofing to cope
with these high voltages.
Lens Markings
The lens marking requirements currently contained in MVSS
108 do not permit the ready detection of a headlamp
improperly equipped with a gas discharge source. Especially
with the current trend towards one clear (nonoptical) lens
being used in front of several different reflectors or projectors
depending on vehicle equipment within and across markets,
it can be very difficult to detect an improper source.
Examples abound; one such example is the headlamp lens on
a MY2001 BMW 3 series, which contains markings applicable
to six variations of the headlamp assembly:
• DOT certification marks for an H7 halogen/reflector
setup
• DOT certification marks for a D2S discharge/projector
setup
• ECE type approval marks for an H7 halogen/reflector
setup for right-hand traffic
• ECE type approval marks for an H7 halogen/reflector
setup for left-hand traffic
• ECE type approval marks for a D2S discharge/ projector
setup for right- or left-hand traffic
• JIS certification marks for Japanese-market vehicles
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