Being dedicated  to seeking the light, I am always on a quest for more illumination. With all the new designer bulbs on the market, I was curious as to which were the brightest available. So I purchased several different offerings from the best  manufactures, and set myself up one night with a "seat of the pants" test lab -a light meter on a tripod situated in the middle of the beam, at various distances from my parked XJ, engine throttled up to 1500RPM to ensure maximum voltage, and one by one tried each bulb, and recorded my findings. No, not very scientific, but when you think about it, it still has some validity I started with a standard 55/65 watt H-4 bulb to establish a baseline, and used a 90/145 watt (clear) bulb as the upper end for comparison.

The outcome was not very surprising to me, though it might be to you. In every test, the clear bulbs shined brighter than the coated ones of the same wattage.

The new blue HID headlights found on some Euro/Luxo cars have spawned a new generation of imitation H-4 bulbs designed to give the appearance of these new super bright lights. All of the coated bulbs like "Super White" "Diamond Blue" etc., use a bluish coating to filter out the yellow spectrum, and give the eye the impression that it is seeing more light output, ...to our subconscious blue light is brighter that white (or yellow) light, but the light meter is not duped by such tricks (just because the Light "temperature" is hotter, doesn't mean that the light output is usable to the human eye when it comes to illuminating objects in the dark). These bulbs claim that a 60 watt bulb is as bright as a 100 watt, and an 80 watt bulb is as bright as a 135 watt clear bulb. Not true. To the eye, they really do look brighter when you look at the light itself, but not to the meter. In fact, the standard 55 watt clear was slightly brighter than the 60 watt Super White. The worst part of all this deception, is safety and visibility for the driver in inclement weather.

In the light spectrum of frequencies, longer wavelengths are better that short wavelengths. Blue being one of the shortest wavelengths, can’t compare with Yellow for power and stamina. Yellow light has a much longer wavelength than Blue light has, so the Yellow light travels farther -both initially and after being reflected- than Blue light does. White and Blue light waves also tend to bounce off moisture particles more than Yellow light waves do, so they don’t penetrated as well. One other big advantage of the Yellow spectrum over the Blue spectrum is that Yellow enhances contrast and color, whereas Blue tends to washout contrast and makes colors appear pale. During night driving, especially in wet weather, contrast becomes a very important element in your visibility, even more important that seeing a 1/4 mile or more down the road. By filtering out the yellow, visibility is reduced in wet or foggy weather, and contrast is reduced in all conditions. This is why fog lights are yellow. Yellow penetrates better, and provides far less reflection when there are moisture particles in the air, and this equals better visibility. The only coated bulbs that are worthwhile, are the Ion Crystal bulbs. They are for fog lights, and produce a yellow light with very little loss in output (much less than a yellow fog light lens), and the coating is close to being transparent to the light output.

So a clear bulb will offer superior visibility over a blue bulb, despite their apparent brightness, especially in inclement weather because it still has the yellow spectrum. And watt for watt, all tests revealed that clear, un-coated bulbs were always brighter than their coated counter-part, despite claims of higher output. True HID light contains a broad spectrum of light because it is a high intensity arc, not a glowing piece of wire suspended in gas. Even though it appears to be blue when looked into, the reflected light the driver sees when an object is illuminated with HID light, is not just blue but a well balanced illumination, because Yellow is still a big part of the HID spectrum. This cannot be achieved by coating an incandescent bulb to filter out Yellow for the sake of looks.

The only bulbs that actually are brighter, are the ones which use a "rarefied" gas mixture (PIAA calls them "EXTRA"), that allow the filament to burn brighter without consuming extra current. However their claims are not quite as good as the real world tests indicate. They are definitely brighter, but the specs say an 80 watt is as bright as a 135 watt. In reality, the 80 watt is somewhere around 115 watts (slightly brighter than a  100 watt, but not quite up to a 120 watt bulb). I feel these bulbs are a good idea for situations where current draw is a concern, but again, avoid the "Super White" coating, it is an expensive waist of money. The key word here is coating, remember, when it comes to light output... "Watts" giveth, ...and "Coatings" taketh away! For the brightest H-4  headlights, there is still no substitute for a clear 90/135 watt PIAA, or a 90/145 watt IPF, or a Hella 100/165 watt. Two other interesting points, once you pass 100 watts, big jumps in power equal small gains in illumination. For example there was no measurable difference between the 135 watt and the 145 watt bulbs, and the 165 watt was only slightly brighter. And secondly, life expentency drops quickly after 80 watts.

On another note, avoid the cheap H-4 bulbs found in the JC Whitney catalog. These are usually made in China, Taiwan or Hong Kong, and are poorly manufactured. They are not designed to withstand the conditions of a vehicle that is used off the road. The vibrations of rough roads, and long burn times at low speeds (no wind cooling) will destroy the filaments in a very short time. Your money is better spent on a high quality bulb like PIAA, IPF, or Hella, sure they cost more, but they last many times longer, so they are actually cheaper in the long run.
 

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