'Well-focused' bulbs

[Klutch9]

I've done a lot of research on headlight bulbs over the years, and the term 'best focused' or 'one of the best-focused' bulbs always gets thrown out there. Now I know that accurate filament placement in any given bulb - 9007, 9006, h11, etc. - is extremely important. But if all SAE/DOT certified bulbs must fall between certain tolerances for filament placement (assuming they all do), how can one be better-focused than another? Isn't light focusing ultimately the responsibility of the reflector or projector housing? I just don't understand how you can take a bulb, even with the highest level of QA/QC, accurately placed filament, etc., put it in any given reflector housing and have it produce a better beam pattern than another bulb meeting equally strigent specs. Enlighten me, as I am very curious

 

[XS650]

The reflector housing is designed to work with a filament of a certain size and shape in a certain location. The bulb spec doesn't require perfection, it allows some deviation from the ideal. Higher quality bulbs have less deviation from the ideal.

 

[Klutch9]

Originally Posted By: XS650
The reflector housing is designed to work with a filament of a certain size and shape in a certain location. The bulb spec doesn't require perfection, it allows some deviation from the ideal. Higher quality bulbs have less deviation from the ideal.


True. But I've noticed some bulbs being advertized with wider beam patterns, farther beam throw, etc. Shouldn't it, in reality, just be advertized as a 'more consistent' bulb? (I understand that the marketing is probably playing up the results a bit too).

 

[mikered30]

You have to read the fine print when discussing further throw, whither, and brighter. Most of the time it is the new bulb at 14 volts vs a used bulb near the end of its life at 12.8 volts, hardly a fair comparison. They also have range for output of + or - 15% which goes in their favor. Marketing at its finest.

 

[UNC017]

Originally Posted By: Klutch9
I've done a lot of research on headlight bulbs over the years, and the term 'best focused' or 'one of the best-focused' bulbs always gets thrown out there. Now I know that accurate filament placement in any given bulb - 9007, 9006, h11, etc. - is extremely important. But if all SAE/DOT certified bulbs must fall between certain tolerances for filament placement (assuming they all do), how can one be better-focused than another? Isn't light focusing ultimately the responsibility of the reflector or projector housing? I just don't understand how you can take a bulb, even with the highest level of QA/QC, accurately placed filament, etc., put it in any given reflector housing and have it produce a better beam pattern than another bulb meeting equally strigent specs. Enlighten me, as I am very curious

Well, specs is specs and reality is reality. All the specs have some amount of wiggle room. It IS possible to place a filament more accurately than the specs require. A classic example I was just reading about is the H4 vs HB2 spec the other day. The H4 spec is an old one- early 70s- and comes from Europe where H4 bulbs were used a lot. In the late 80s to early 90s when the US started allowing replaceable-bulb headlamps, US regulators took a look at the H4 spec and decided that, since the US still required blind mechanical aiming of headlamps, the H4 spec would allow too much variation in beam pattern once installed in lamps and having the lamp and bulb tolerances "stack" and increase error. The HB2 spec came about as a result- the bulb is EXACTLY the same to all appearances as an H4, but the filament placement and shape are more tightly constrained, as are the demands on luminous flux and input power. And, theoretically, lamps would be consistent enough to be aimed by mechanical means rather than by looking at the beam and placing it correctly. Now most "H4" bulbs are actually manufactured to HB2 tolerances.

However, you're right in that the reflector is probably the source of more trouble than the filament. A super-expensive ultra-precise filament won't make a [censored] reflector assembly work much better. And besides, most bulbs that advertise better "focus" are probably blue-tinted, offshore-manufactured snake oil anyway and are actually far WORSE than generic replacement GE or Philips bulbs are.

 

[Smokescreen]

If you look at the filament structure, it is a series of coils held up by two posts. Filament uniformity and coil spacing within the filament are what determines better focus. This directly translates to how the hot spot affects the projected beam and brighter areas within that beam. More precise controls are needed to place the hot spot giving focus to claims of 30% brighter straight ahead or off to the sides etc. We are talking of micrometers variances = big differences to the beam characteristics.

 

[Hokiefyd]

You can change the pattern with filament placement, and this is more feasible with older bulb specifications that allow for a greater tolerance in the filament placement. You can also get different optics by lengthening or shortening the filament. If you closely examine a Sylvania Xtravision, for example, with a standard OEM-spec long life bulb, you'll see that the Xtravision's filament is physically smaller. This creates more of a "point source" of light than a physically larger filament and can sharpen the edges of the beam pattern and can even change the beam pattern if the filament is made physically smaller and shifted forward or rearward or up or down, spatially, within the bulb glass.

 

[UNC017]

Originally Posted By: Hokiefyd
If you closely examine a Sylvania Xtravision, for example, with a standard OEM-spec long life bulb, you'll see that the Xtravision's filament is physically smaller. This creates more of a "point source" of light than a physically larger filament and can sharpen the edges of the beam pattern and can even change the beam pattern if the filament is made physically smaller and shifted forward or rearward or up or down, spatially, within the bulb glass.


Very good point- by shrinking the filament they get "wiggle room" inside the box defined by the spec.

Of course the tradeoff is far shorter life, since the small filament runs significantly hotter to produce the same amount of light. And that's also part of how they get the color temperature higher, too. And in the case of the Xtravision, they probably don't even manage to stay within the specs. Sylvania has really gone in the pooper over the past 15-20 years. These days I generally pick Philips, Narva, Osram (which ironically is Sylvania's parent company!), or GE (depending on the application).

 

[Hokiefyd]

Many of the Xtravision bulbs are actually made by OSRAM. I have Xtravisions in both vehicles (HB2 in the Honda and H11 in the Acura) and both are made in Germany by OSRAM.

 

[UNC017]

Originally Posted By: Hokiefyd
Many of the Xtravision bulbs are actually made by OSRAM. I have Xtravisions in both vehicles (HB2 in the Honda and H11 in the Acura) and both are made in Germany by OSRAM.


Yes, its a mixed bag with the bulbs more commonly used in European cars tending to be sourced from Osram and the same as Osram-branded parts. Not so if you need a 9007 (which is a cruddy format to start with and only gets worse if the manufacturer cheaps out in building it).

And its actually the Silverstar line I'm thinking of that is notoriously bad, not so much Xtravision.

 

[Klutch9]

Originally Posted By: 440Magnum
Originally Posted By: Hokiefyd
Many of the Xtravision bulbs are actually made by OSRAM. I have Xtravisions in both vehicles (HB2 in the Honda and H11 in the Acura) and both are made in Germany by OSRAM.


Yes, its a mixed bag with the bulbs more commonly used in European cars tending to be sourced from Osram and the same as Osram-branded parts. Not so if you need a 9007 (which is a cruddy format to start with and only gets worse if the manufacturer cheaps out in building it).

And its actually the Silverstar line I'm thinking of that is notoriously bad, not so much Xtravision.




Agreed, 9007 bulbs are awful. Unfortunately, 3 out of 5 cars I've owned have had the 9007, and one had the 9004 (the 9007's evil, even more sub-par cousin). Thankfully, my last car had the 9006/9005 setup, which was good, plus it's easier to make it even better with HIR bulbs.

 

[HTSS_TR]

The 9004 on the '91 Tracer is really weak.

 

[Hokiefyd]

Originally Posted By: 440Magnum
Originally Posted By: Hokiefyd
Many of the Xtravision bulbs are actually made by OSRAM. I have Xtravisions in both vehicles (HB2 in the Honda and H11 in the Acura) and both are made in Germany by OSRAM.


Yes, its a mixed bag with the bulbs more commonly used in European cars tending to be sourced from Osram and the same as Osram-branded parts. Not so if you need a 9007 (which is a cruddy format to start with and only gets worse if the manufacturer cheaps out in building it).

And its actually the Silverstar line I'm thinking of that is notoriously bad, not so much Xtravision.


You're right about that. Even the standard (non-XV) Sylvania H11 bulbs are OSRAM from Germany. I can't speak to the Silverstar line...never bought one.