Headlight Technology
The Tungsten-Argon Headlight
One of the earliest headlight technologies to emerge after the acetylene lamp days was the tungsten-argon headlight. This design was based on a large glass housing called a sealed beam, thus it was often called the sealed beam headlight. At the center of this glass enclosure was a heat-resistant tungsten thread (filament). This special wire was heated by passing electricity through it, until it got white-hot, or "incandesced." In early units, a vacuum sealed inside allowed the filament to glow very bright yet not burn up. Later examples used Argon gas instead, to slow filament deterioration. The tungsten-argon headlight has a big drawback however, and that is its low efficiency. The design produces more heat than light, so the electrical energy is mostly wasted. This inefficiency makes tungsten-argon headlights look very yellow, because the total light output is low, and the yellow parts of the light spectrum therefore show visibly. The output also gets worse with age, because the filament in this design is always eroding. Its tungsten dissipates and is slowly deposited onto the headlight’s glass, the deposit increasing and reducing the light’s output all the while.

The Tungsten-Halogen Headlight
During the late 1970s the tungsten-argon headlight was replaced with a better design, the tungsten-halogen. Like its predecessor, the tungsten-halogen design also uses a tungsten filament. However, in the halogen headlight, this filament has less resistance, causing more current to flow through it, heating it up more. Also, it is enclosed inside a replaceable tiny bulb made of quartz, so chosen because glass would melt, being so close to the extra-hot filament. (Though later versions used high temp glass, the design is still often called the quartz-halogen.) The gas inside the bulb is not Argon but a gas from the halogen family, often iodine, and under very high pressure to increase the bulb's temperature even further. The iodine gas combines with the tungsten of the filament at this high temperature, permitting the dissipating filament’s metal to redeposit onto the filament, extending the filament's life and preventing the permanent clouding of the bulb’s inner surface. Combined with the higher current, this produces a brighter light, for a longer time. However, the tungsten-halogen headlight gets its extra light mostly from extra heat, partly due to its high current and partly due to its hotter design. Older tungsten-argon equipped bikes are definately taxed electrically when running halogen bulbs. In any application, the bulb runs so hot it can reach over 450^o F..

The High Intensity Discharge (HID) Headlight
The newest technology is the non-incandescent, high intensity discharge (HID) headlight. The HID addresses the problem of the incandescent headlight's low efficiency, by doing away with incandescence altogether. The HID headlight was adapted from industrial large-area lighting, such as the lighting in sports stadiums. Unlike other headlights, the HID produces light by throwing a high-voltage arc into a special gas. The gas reacts to this jolt by producing light. Because it’s not an incandescent design, the HID’s electrical efficiency is more than three times that of other headlights. With no glowing filament, the headlight operates much cooler and failures are much less frequent. More importantly, the HID headlight produces three times as much light, and much whiter light than other headlights, resulting in greatly improved visibility.

However, though found on high-end luxury cars and avalable in aftermarket form, cost and legal issues have delayed the HID's introduction by the powersports OEMs. The expense is a major factor, enough to give even Mercedes pause at first. The adaptation of HID technology to vehicle use required solving several technical problems, all of which added to the cost of manufacturing. One such problem was warm-up. Stadium HIDs take 5~10 minutes to warm up, an unacceptable situation on a motor vehicle. To compensate, expensive Xenon gas and sophisticated electronics are used in HID headlights, and aa result, automotive HIDs reach 75% of full their intensity in just a few seconds. However, the really big issues among powersports vehicle manufacturers are the legal ones, most of which center on the individual’s ability to adapt to the new technology. For example, the HID headlight has a very sharply defined light envelope. Unlike the tungsten-halogen’s soft light edges, the HID’s beam leaves a sharp line between what is illuminated and what is not. The result is startling to the first-time user. Objects dramatically appear and disappear at the edge of the beam as the vehicle traverses irregularities in the roadway, producing an uneasy feeling. It takes getting used to. However, the most publicized legal problem is the HID’s effect on other drivers. When looked on directly, HIDs have a blue appearance, though the light is actually extremely white. This is a consequence of the HID’s brightness -- the usual yellow cast produced by other headlights is almost totally absent in the HID. As a result, HID light appears slightly blue alongside other headlights. (Blue and yellow are color opposites. When yellow is removed from the color spectrum within white light, blue is enhanced.) This blue cast would be harmless except that it has an effect on eyesight that is disconcerting. Normally, when bright light enters the eye, the pupils contract to compensate, and glare is avoided. However, if you have ever been to the eye doctor and had your eyes chemically dilated, you know that afterward the eye can’t compensate, and even moderate light is glaring. Unfortunately, the blue that accompanies the HID’s light has the same effect -- it interferes with pupil contraction. It prevents the eye from protecting itself, resulting in severe glare, especially at night. Though completely legal, new government regulations concerning HIDs are expected soon in response to complaints from various quarters. However, history records that sealed beam and then halogen headlights met just as much opposition. Despite these challenges, the aftermarket is already enjoying great success with HID headlights. Many powersports OEMs are preparing to introduce them as well.

"Blue" Headlights
But what of other blue headlights? The aftermarket is absolutely teeming with blue headlight bulbs today. Most of them are HID headlight emulators. These "cool blue" fake HID lights are merely tungsten-halogen bulbs with a blue tint added, producing a bluish headlight. Unfortunately, blue is the shortest light wavelength. Consequently, this blue light dissipates quickly, producing more glare from fog, rain, and snow. For this and other reasons, non-white headlights are illegal for road use in the U.S., Canada, and many other countries. There is however another, legal, version of the "blue" headlight bulb. This one has a gold color on its glass. The coloring is not a tint but a special color filter, which blocks the yellow in the bulb's light, producing a whiter output. The reduction of the halogen's yellow output brings as a byproduct a slightly blue cast, just as the yellow's inherent absence in the HID headlight makes its color slightly blue. However, the two systems get their blue byproduct from different sources, and unlike the HID, the overall light from this &qiot;ultra-white&qiot; tungsten-halogen bulb is sharply reduced. The major color in the incandescent headlight’s light remember is yellow. Therefore, with the yellow spectrum blocked, less light reaches the road. These lower-output bulbs are, surprisingly, legal because they conform to the government regulations specifying white light. Unfortunately, the light they output is actually less bright than that from standard tungsten-halogen headlights.

"Xenon" Headlights
To further confuse the issue, some companies are advertising "Xenon" headlight bulbs. These aren't anything special. They are merely tungsten-halogen bulbs that have xenon added to their halogen gas. Xenon is the best gas to have inside an incandescent bulb. It has larger atoms that are better at bouncing evaporated tungsten atoms back onto the filament, with the result significantly improved bulb life. However, this is not a special bulb at all, as all of the newest tungsten-halogen bulbs are made to this specification, not just a few company’s offerings. Even more of a problem is the confusion that results from the use of the word "Xenon" for different kinds of headlight bulbs. Late model (H7) tungsten-halogen bulbs are mistakenly called Xenon, as are also HIDs, even though that is not the correct name for either of them, and they are completely different bulbs. One has a filament and the other doesn't.

Summary
To summarize, there are three kinds of so-called "blue" headlight systems. The HID, which started the blue craze, is the real McCoy. It has a legitimate, slightly blue (actually purple) cast due to its otherworldy whiteness, and is therefore not actually a blue headlight, but extremely white and bright. HIDs are legal, and are showing up on motorcycles, particularly offroad machines. The second type, the "cool blue" headlight bulb, is an HID fake, and that's all it's meant to be and can be. It is illegal in all of the Western world however, because it is in fact a colored headlight. Finally, the third type, the "super white" headlight bulb, is an attempt to brighten the headlight by removing its yellow range. Unfortunately, in the process, though the light is whitened to the point of having a slight blueness, the output is actually weakened. Though legal, this third category of headlight bulb isn't really safe. Now you know. Got any salsa...?