Whenever HIDs are mentioned (especially aftermarket) there is always a lot of excitement and debate on the forums. I thought I would post on here with some measurements taken from a range of light sources. This data is from the Consumers' Association (who publish Which? magazine) and was published March 2010. The car used for the tests was a new model Vauxhall Astra fitted with either OE HID's or H7 Halogen bulbs. The light intensity readings are in Lux.

The readings are dipped beam intensity (Lux) and main beam intensity (Lux) for the different types of light sources.

Factory OE H7 Halogen.....................91.........................48

Factory HID...........................................164......................131

Philips X-treme +80%........................102......................62

Halfords SuperBrilliance +50%..........90......................62

Halfords Standard H7...........................78.....................64

Osram Nighbreaker +90%................97........................63

Bosch Pure Light................................141......................55

So the best halogen light source seems to be the Bosch Pure. These cost about £22 a pair. They are not far behind the factory HID's. It is fair to assume that aftermarket HID's would come somewhere above the Bosch Pure and below the factory HID's. The HID's really seem to win out on main beam performance where they are significantly brighter than halogens.

Sorry about the formating - mods please feel free to change!

Problem with main beam or driving light HIDs is the long warm up period which makes them impractical on the road. Bi-xenons address the problem I guess by moving the dipped beam pattern.

Do people find that the HID (daylight) bulbs are very dazzling even on dipped beam with oncoming traffic :'(

Excellent post!