Taken from: http://lighting.mbz.org/tech/info/bulbs/superwhites/

Also check out: http://lighting.mbz.org/tech/info/bulbs/blue/

In short, get the best focusing headlamp assembly out there, and then get a reputable bulb.

:-) neil
1988 360TE
soon 1993 500E (BARNEY)
======================

PIAA's wattage equivalence claims ("55w = 85w", etc.) are very misleading. They cannot be verified with proper laboratory equipment, and they CERTAINLY aren't true when compared with real overwattage bulbs on the road. Here's the full scoop:

CLAIM: PIAA "SuperWhite" bulbs produce 85W of light from 55W of electricity

REALITY:
PIAA "Superwhite" bulbs produce exactly the same amount of light as any other bulb in a given bulb format (9004, 9005, 9006, H4, etc.), plus-or-minus 15 percent (which is the US FMVSS 108 Part 564 tolerance for variations in luminous intensity from headlamp bulbs).

The "55W = 85W" type claims are a sham. Here's how these kinds of pretend wattage numbers are cooked-up: The filaments in PIAA "Superwhite" bulbs are wound on a larger mandrel than regular filaments, so there are fewer filament coils, of a larger diameter. When these bulbs' luminous intensity is measured using the appropriate device (called an integrating sphere), they come up within the FMVSS 108 Part 564 tolerance range for whatever bulb type is being tested--no more. (If they didn't, they would not be permitted to be marked DOT, and they are, so they do.)

When a bulb with such a modified filament stack is placed in a headlamp, the different dimensions of the filament alter the beam pattern. In most US-specification headlamps, what this does is reduce the size of the central "hot spot" of the beam and put more light in it, while taking away light above, below, to the left and to the right of the hot spot. Then the PIAA marketeer comes up with his light meter, sticks it in the hot spot of the beam, and says "Nifty! The hot spot is almost as bright as it would be with an 85W bulb!" and rushes off to order-up a new batch of boxes festooned with "55W = 85W" banners. Then Mr. Consumer comes along, plunks-down some $70 (!!) for a pair of these bulbs, puts them in, and though his headlamps look "whiter", he has just screwed himself. How?

Well, the reason why many people find many US-specification headlamps in need of upgrading is because many US-spec
headlamps have insufficient foreground light, which creates a "black hole" on the road in front of the car. There's often insufficient lateral light (left and right) to see critters or people before they run into the road. The "hot spot" creates a narrow tunnel of light that disappears "out there somewhere". By making the hot spot smaller, this narrow tunnel of light gets smaller. By taking away (already scarce) light from the foreground and sides, the situation is made worse.

CLAIM: PIAA "Superwhite" bulbs produce light that is whiter and brighter than regular bulbs.

REALITY:
It is a mistaken notion that "whiter" and "yellower" qualities in the white light of a headlamp have any direct link to the amount or usability of the light. PIAA capitalizes on that mistaken notion to sell their bulbs. The "higher light color temperature" trumpeted by PIAA is created by a purplish-tinted glass bulb globe. It's not a dichroic coating like the "diamond blue" junk, but it is a tint, and as such physically must subtract from the available light. Remember, color temperature is independent of the amount of light, and there is absolutely *zero* evidence that light of a higher color temperature is better than light of a lower color temperature for driver performance at night. A 4-watt flashlight bulb dipped in the purple coating applied to Piaa "Superwhite" bulbs would look "whiter", but produce less light. And so it is with these headlamp bulbs.

People seem to have the notion that the eye is more sensitive to light of higher color temperature. This is probably as a result of claims made by car salesmen trying to sell HID headlamps more than anything else; it's false. The eye is not more sensitive to the blue cast created by the subject bulbs. There have been several studies done showing improved driver performance (due to improved vision at night) with headlamps of LOWER color temperature (less blue, more yellow). Color perception is much better under lower color temperatures (within the IEC "white" boundaries, of course), and the acuity of the human eye is really quite lousy under light colors that even begin to approach "blue".

CLAIM: "I've got pictures that prove the brightness difference!"

REALITY:
You have proof of nothing. Not only can photographs not accurately record or represent the intensity of a lamp or beamcaster, but photos placed on the web are even less true to reality. At best, what you have is something of an illustration of the color difference between the regular bulb and the "Superwhite".

BOTTOM LINE:
The laws of physics are the laws of physics. They don't bend even for PIAA's advertising department. There is no way to get "85 watts of light for 55 watts of electricity", unless the light meter you use happens to go spastic when hit with blue-tinted light. There is no seeing advantage to these "Superwhite" ("ultrawhite", "hyperwhite", etc.) bulbs, and quite often a disadvantage. They aren't as bad as the "ion blue" junk used by poseur kids who want to pretend they have HID headlamps, but they're not magical.