Claims ("55w = 85w", etc.) made for "Superwhite" type bulbs are very misleading. They simply aren't true. Here's the full scoop!
CLAIM: "SuperWhite" bulbs produce 85W of light from 55W of electricity
REALITY: "Superwhite" ("Hyperwhite", "UltraWhite", "Platinum", etc., basically any bulb advertised as being "whiter" than normal) bulbs produce more glare and less seeing light than standard bulbs.
The "55W = 85W" type claims are a sham. Here's how these kinds of pretend wattage numbers are cooked-up: The blue or purple filtration coating on the glass tints the light so that it is "whiter". Most bulbs that actually produces more light (i.e., higher-wattage bulbs) also burn with a whiter color than standard-wattage bulbs. With these color-coated bulbs, only the light color, and not the actual light output, imitates a high-power bulb. There is no seeing advantage to "whiter" light, though some people seem to think that others will look upon headlamps so equipped and go "Wow, cool!". Why they believe anyone else cares what color their headlamps are is anybody's guess.
A major reason why many people find many US-specification headlamps in need of upgrading is because many such headlamps have very low levels of 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", with no visual cue to where the beam (and therefore the driver's seeing range or "preview") ends. But these headlamp performance aspects are governed by the optics of the lamp, not by the color of the light. Bulbs with blue or purple tinted glass never improve the performance of your headlamps. They may leave it relatively unchanged, or they may severely reduce it, but they never improve it.
CLAIM: "Our bulbs produce the whitest and brightest light on the road!"
REALITY: "Brightness" is like "Loudness". It's a subjective perception. Is Metallica " louder " than Bach? Most people would say so. That's why audiologists use an objective measurement, Sound Pressure Level, rather than subjective quantities like "volume" and "loudness". And so it is in the science of light. "Bright" and "Dim" are subjective perceptions. Intensity, measured in any of several precisely-defined and scientific ways, is the only real way to gauge or compare output of a light source or performance of a lamp equipped with a light source. A 4-watt flashlight bulb dipped in the purple coating applied to these tinted headlamp bulbs would look "whiter", and might look "brighter", but would produce less light. And so it is with these headlamp bulbs.
The reason why the scam fools people into thinking their headlamps really work better has to do with the interaction of light that is tinted blue (to any degree) with the human eye. This kind of light has been shown in rigidly-controlled scientific studies to create almost 50% more glare than untinted light from a bulb with clear glass. But there's no 50% increase in seeing to go along with the extra glare; there's no increase in seeing at all, and in most cases there is a moderate reduction in actual seeing light. More glare, less seeing: Everybody loses.
CLAIM: Many of these bulbs are sold with claims of specific "color temperature" (e.g. "5000K"). Often, these ratings are accompanied by text to the effect that higher color temperatures are "close to natural daylight".
REALITY: Color Temperature is a real measure, but it is being improperly used to claim improved seeing. Legitimate bulb manufacturers do catalogue the color temperature of their products in technical literature not usually distributed to consumers, because scientists and engineers can use it as a convenient proxy indicator for filament luminance. But it has no predictive value for the performance of an automotive headlamp, nor does it indicate how well you'll be able to see. The idea being sold with these "Kelvin ratings" is that the light is closer to natural sunlight. As with many sales claims, there is a small kernel of truth here, but it's cancelled out by the smoke and mirrors. Noonday sunlight does have a much higher color temperature than most uncoated headlamp bulbs, but there are a great many other differences between sunlight and headlamp light, as well. Not only that, but the Color Temperature rating is really valid only at extremely high light intensity, such as that produced by the sun. At the lower intensities produced by most electric lamps including headlamps, the rating no longer says much about the light, but only allows a limited, referential comparison of different light colors. The tinted bulbs' poor imitation of the color of sunlight does not mean that the headlamp output is "just like sunlight", or anything even close. As with the wattage equivalence claims discussed above, a color-based comparison is being used to imply an intensity and seeing-ability comparison that does not exist. This also addresses the related claims that
CLAIM: "I've got pictures that prove the brightness difference!"
REALITY: Photographs, film or digital, cannot accurately represent the intensity of a light or lamp, because of the many significant differences in the perception of light by the human eye vs. the camera. By simply adjusting the exposure settings or white balance, virtually any bulb or lamp can be "shown" to be superior to virtually any other.
BOTTOM LINE: The laws of physics are the laws of physics. They don't bend even for the highest-paid advertising agency. There is no way to get "85 watts of light for 55 watts of electricity." Tinted bulbs aren't better.
Daniel Stern Lighting (Daniel J. Stern, Proprietor)
Copyright ©2003 Daniel J. Stern. Latest updates 10/12. No part of this text may be reproduced in any form without express permission of author. Permission to quote is granted for the purposes of communication with the author.