High Intensity Discharge lamps

A High Intensity Discharge, or HID, is an aftermarket upgrade people fit to improve the lighting on the Elise.

Xenon or HID lamps are the bright white lamps you normally find in the newer generation cars. Although these lamps draw less current then the OE halogen bulbs, the light output is increased by approx. 3 - 3.5x over a Halogen bulb.

Besides the colour temperature of these lamps is different. Some kits quote around 6000 Kelvin which is experienced as near daylight. The advantage of this colour temperature is a more relaxing view of what's in front of you. Besides, road marking will reflect better.

It is a common misconception that the higher the K (Kelvin temperature) the brighter the bulb. In fact it is the opposite. The K rating is inversely proportional to the light output.

The actual bulb looks like a small glass bubble. The bubble looks empty, but is filled with Xenon gas. (hence the reason why some people call these lamps Xenon lamps) The Xenon gas is used as the conductor. Applying 12 Volts to this conductor wouldn't start the lamp as the Xenon gas needs a higher voltage to start. To start the lamp, you need to apply approx. 24000 Volts, but when the lamp heats up the voltage is lowered to approx. 85 Volts.

Comparing the two: (based on a H1 (=Elise S2) base) Halogen HID Wattage (W) 55 / 35 Candela (CD) 67500 / 202500 Lumen (Lm) 1550 / 3200 ColourTemp (K) 3200 / 6000

Comparison

The first 3 pictures by Janitor show direct comparison taken in identical light with a flash. (The original lights on left, HID & LEDs on right) But they are for an S2. The subsequent 6 pictures by Grinnders show the comparison between standard Halogen and 4000k HID on an S1 in standard H4 units.