Now there's a man who knows his lights!
Daniel Stern Lighting wrote:
> Sylvania Silverstar bulbs have a blue filtration coating on the glass.
> There is no such thing as a blue-coated headlamp bulb that gives
genuinely
> better performance than an uncoated bulb. All colored filters "steal"
some
> of the light passing through them -- you cannot have filtration *and*
> still have all of the source light available for use after it's passed
> through the filter.
>
> There are legal regulations on the minimum and maximum light output
> allowed for each different headlamp bulb type. The range for most types
is
> nominal value plus or minus 15 percent (some have a narrower plus-minus
10
> percent allowable range). That means a bulb type -- for instance, the
low
> beam of a 9007 -- with nominal output of 1000 lumens is legally
permitted
> to produce between 850 and 1150 lumens. This, in turn, means that five
> different 9007 bulbs, all producing _legal_ output, do not necessarily
> produce the _same_ output. For maximum headlamp performance (maximum
> seeing) you want the highest lumens.
>
> There are also legal regulations on the maximum power consumption
allowed
> for each different headlamp bulb type. For many nominally "55 Watt"
types
> (again, such as the low beam of a 9007), the maximum allowable power
> consumption is around 62 Watts at 12.8 Volts. This means manufacturers
> cannot ramp up the wattage in an effort to get higher headlamp
performance
> (near the top of the allowable lumens) *with* the light-stealing colored
> glass. So they put in a high-luminance filament coil that is,
effectively,
> designed for use at a slightly lower than normal voltage (typically 11.9
> to 12.1 instead of 12.8 to 13.2). This is called "overdriving" the
> filament: It puts out a lot of light when run at normal voltages, but
its
> lifespan is very short compared to a filament that isn't being
overdriven
> -- and all the extra light being produced is absorbed by the colored
> coating, so in the end at best you have the lumens of a standard bulb,
and
> in most cases the actual lumens are less than with an uncoated bulb.
>
> These colored bulbs, whether it's Sylvania's Silverstar, Wagner's
> Tru-View, General Electric's Super Blue, PIAA's Xtremewhite, etc., do
not
> produce "blue" light. They tint the light *in the direction of blue* to
> produce a visual appearance that is "whiter" and "brighter". "Brighter"
> does not mean there's more light -- it's a subjective visual appearance
> only. More light is indicated by the term "more intense", which you'll
> notice the marketers of blue bulbs stay away from, because these bulbs
do
> not make your headlamps more intense. You may also see reference to
these
> kinds of bulbs producing light of a "higher color temperature". That's
> another way of saying the same thing: The light is tinted in the
direction
> of blue.
>
> There's been a fair amount of research done on the effects of these
bulbs
> on all aspects of headlamp-related phenomena (seeing, glare, etc.).
> Sullivan and Flannagan of the University of Michigan Trans****tation
> Research Institute, and others, have found that there is no improvement
in
> seeing with either the Sylvania-type (blue coated) or the Wagner-type
> (Neodymium Oxide) colored bulbs, but -- at equal *intensity* -- the
> colored bulbs produce significantly more glare (nearly 50% more) than
> bulbs with clear glass:
>
> Sullivan, J. M.; Flannagan, M. J. 2001. Visual effects of blue-tinted
> tungsten-halogen headlamp bulbs. Michigan University, Ann Arbor,
> Trans****tation Research Institute, Human Factors Division. 28 p.
Sponsor:
> Michigan University, Ann Arbor, Industry Affiliation Program for Human
> Factors in Trans****tation Safety. Re****t No. UMTRI-2001-9. UMTRI-94291
>
> A copy of this study can be had fairly easily by contacting UMTRI (
> www.umtri.umich.edu ). That 94291 number at the end of the cite is the
one
> you need.
>
> It is also worth considering as we head into winter that light of a
> *lower* color temperature is better for driving in rain, fog or snow.
Not
> because such light "penetrates the snow (fog, rain) better", as has
often
> been erroneously argued in sup****t of yellow fog lamps, but because of
how
> the human eye processes different light wavelengths (colors). See:
>
> Bullough, J. D.; Rea, M. S. 2001. Driving in snow: effect of headlamp
> color at mesopic and photopic light levels. Rensselaer Polytechnic
> Institute, Lighting Research Center, Troy, N.Y. 9 p. Lighting Technology
> Developments for Automobiles. Warrendale, SAE, 2001, p. 67-75. Re****t
No.
> SAE 2001-01-0320. UMTRI-94232 A10
>
> Bottom line, some people find the appearance of these "extra white"
> headlamps more pleasing than the appearance of untinted headlamps, but
> they do not help you see, they cause more glare, they work against you
in
> bad weather, and their lifespan is comparatively short.
>
> Most of the manufacturers offer headlamp bulbs that have higher-output
> filaments _without_ any light-stealing color coating. These tend to run
> right at the high end of allowable lumens. They're more popular in
Europe
> than in North America, but North American examples are Sylvania
> Xtravision, Wagner BriteLite, GE High Output, Philips High Visibility,
> Candlepower Bright Light, Narva Rangepower, and -- confusingly -- Osram
> Silverstar, an extra-high-output *uncolored* bulb line sold primarily
> outside North America.
>
> Finally, some comparative bulb test results. AutoExpress finally
released
> the results of their new H4 (=9003, =HB2) bulb tests.
>
> Standard and blue bulbs ("Osram CoolBlue" is what is currently sold in
> North America as "Sylvania Silverstar"):
>
>
http://www.autoexpress.co.uk/product_test/product_test_story.php?id=39920
>
> "Plus 30" high efficiency bulbs ("Osram Super" is what is sold in North
> America as "Sylvania Xtravision", while "Philips Premium" is available
in
> North America as "Wagner BriteLite" and "Candlepower Bright Light"):
>
>
http://www.autoexpress.co.uk/product_test/product_test_story.php?id=39919
>
> "Plus 50" ultra high efficiency bulbs (Osram Silverstar is available in
> North America as Candlepower Super Bright Light, or -- like the Philips
> VisionPlus -- can be ordered from one of the overseas websites that
****ps
> worldwide):
>
>
http://www.autoexpress.co.uk/product_test/product_test_story.php?id=39917
>
> The AutoExpress website will let you view up to two articles before it
> wants you to "register" -- throwing phony info at it will make it shut
up
> and let you see more stories. They've done similar tests of other bulb
> formats over the last few years (regrettably no longer on the site) and
> come up with very similar results.
>
>
> Daniel J. Stern
> Standing Appointed Member
> National Academy of Sciences
> Trans****tation Research Board
> Visibility Committee
>
>
>
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