Very Very Very long answer to the halogen vs. xenon question - you've been warned
Everything you wanted to know about halogen and xenon and were unfortunate enough to ask when I'm trying to avoid doing laundry....
ok you got two easily confused technologies here. There are halogen bulbs with a shot of xenon that acts like a blanket on the halogen and makes it butn hotter, and there are HID xenon lamps, which in my opinion at least are far superior.
As to the HID xenon -
this link is for automotive HID headlights, but I reckon the results still apply to bike applications. For the linkage impaired, bottom line is standard halogen lamps (and those with a xenon mix) use a filament, xenon (High Intensity Discharge) uses an arc created in the gas between two electrodes. HID uses less power, lasts 10 times longer, has 3 times the light output, and a higher color temperature.
Now... color temperature is not the same as "heat". It's just a linear way to measure light output. Low end is the warmer red/yellow spectrum, high end is the 'cold' end... blue. To get technical, the color temperature is the temperature to which one would have to heat a theoretical 'black body' (no jokes, Nexus) to produce light of the same visual color. A candle is around 1500 Kelvin. A regular headlight is around 3400K, xenon around 4500K and noon day sun (assuming anybody up north is seeing that) is around 5500K. Oddly enough, and overcast sky is around 6500K. A clear blue sky can ranges from 9000K all the way up to 12,000K. Chart meant for photography purposes can be seen
here.
Back to the halogen/xenon mix lamps: the more xenon is added, the whiter the light gets. There are 3 standard levels, +30 (raises color temperature to about 2600K), +50 (raises to about 3000K) and +100 (raises to about 4000K). Actually, enginerds (sorry Meat
) have found the adding more than 27% xenon returns no further benefit. Adding the xenon makes little or no more light, it just makes the light whiter. The +30 and +50 bulbs turn out about 7% more lumens, and the blue coating on the 100+ negates that. The blue quartz bulb (or blue coating on the inside of the bulb) is supposed to block out some of the visual spectrum that causes eye strain. The blue tint oncoming drivers see (and frequently hate) is invisible to the driver, who sees only white light in front of him.
Energy supplied... increase with halogens may be slight, but probably not significant. xenon HIDs may pull an initial 15amps for less than a second to fire up, but then quickly settling down to 2 - 3 amps.
As to heat... yes, a halogen or halogen/xenon mix lamp will burn quite hot. Frequently hotter than the manufacturer planned for in designed light housings. A true HID xenon arc lamp will actually burn cooler - it converts the energy it's fed into light more than heat. Physics, man.
ok - I'm done.
