Originally Posted by DtownJK

Changed the bulbs out to Silverstar Ultra 4100K and they work great and no blue tint at all. Very white and really bright.

Originally Posted by Scheinwerfermann

Three main characteristics of any light are its spectral power distribution (SPD, the absolute presence and relative prevalence of the different wavelengths that humans can see), its colour rendering index (CRI, the fidelity with which the light reveals colours, compared to standardised sunlight conditions), and its correlated colour temperature (CCT, applicable only to white light, basically whether the light is "cool" or "warm" in appearance).


SPD:

The visible portion of sunlight is a continuous spectrum from red to violet, with no gaps. The visible portion of a glowing filament (which is a blackbody radiator) is likewise a continuous spectrum from red to violet, with no gaps. The spectrum of an HID lamp is a series of peaks and valleys. The light is superabundant in certain wavelengths (colours), relatively deficient in others, and absolutely deficient in still others. So from the standpoint of SPD, halogen headlamps actually are much closer to sunlight than HIDs. Which is better? Well..."better" is tricky to define here, because it really depends on what exactly we're trying to do with the light we're creating. In general, a continuous spectrum (rather than a peaks-and-valleys spectrum) is better, because it makes it easier to get a higher CRI, which I'll get to in a moment. But that's definitely not an inviolable rule! Sometimes (as for example when driving through fog or snow) we want to filter out a portion (blue to violet, in this case) of the spectrum. And for general illumination, there are many excellent discontinuous-spectrum lights (fluorescents, HIDs, LEDs, etc.), though this is not an either/or situation. The old fluorescent lights and mercury vapour street lamps produced yucky-looking light because of gross excesses and deficiencies (peaks and valleys) in the spectrum, but today's phosphor and halide technologies are giving us fluoro, HID, and LED lights that may have a peaky spectrum, but contain enough of the various wavelengths to produce a good-quality light. It is worth noting here that there is no such a thing as "full-spectrum" light. The term is used by marketers of everything from headlight bulbs to seasonal affective disorder lights to reading lamps to new fluoro tubes for your kitchen, but it means whatever any particular marketeer wants it to mean. There is no standard definition — not even close.



CRI:

Obviously, not all sunlight is the same, so a set of conditions has been standardised. In greatly simplified terms, the conditions can be understood as "noonday sun on a clear day". This is considered to be a CRI of 1.00 (sometimes stated as "100"). There is no light of CRI higher than 100, and a higher CRI is always better than a lower one except in certain very specialised lighting tasks (as for example in photographic darkrooms or in situations where ordinarily-tangential factors such as preservation of night vision, rather than ordinary factors like effective illumination, are the priority). A properly-fed tungsten-halogen filament lamp with a colourless glass or quartz envelope has a CRI of between 0.9 and 0.99 ("90" and "99"). Current-production automotive HIDs have CRI of between 0.7 and 0.74 ("70" and "74"). So, again, from the standpoint of CRI, halogen headlamps are closer to natural sunlight than HIDs.



CCT:

This is measured in Kelvins (not "degrees Kelvin" as is sometimes incorrectly stated), and is directly keyed to the kelvin temperature of a blackbody radiator. In this scale, there is no such thing as "better/worse", just different/same/similar. The standardised sunlight conditions described above are considered to have a CCT of 6500K. Automotive HIDs (real ones, not ones that have been jiggered to produce bluer-than-standard light) are between 4000K and 4500K. Properly-fed tungsten-halogens are between 3100K and 3450K. So, in this respect, automotive HID headlamps are closer to sunlight.

Now, what are the safety performance implications? Enough research has been done to show that the poorer CRI of HID headlamps is of no safety consequence. Stop signs still look sufficiently red, for example, and guide signs still look yellow enough. The SPD might be causing some glare-related problems. Automotive HIDs have a high spike in the blue-violet region, and there's pretty good evidence that just as some people are glare-sensitive and some are not, some people are blue-sensitive and some are not. This is not a medical condition or disability, it's just a human variance like nose size or eye colour. There's also prety good evidence that at any given intensity, headlamp light with a higher proportion of blue light causes more glare than headlamp light with a lower proportion of blue in it. There is competing evidence, however — yes, academic researchers do compete with one another, with theories and studies and data instead of long-jumping frogs or whatever — suggesting that a higher blue content improves certain aspects of drivers' night vision. Scientifically this one hasn't been shaken all the way out yet, and it's possible both effects might exist simultaneously to some degree. From a marketing perspective, the question is moot; the decision's been made to push more and more towards the direction of bluish-white car lights.

Up to now, most of the research has effectively conflated CCT and SPD, because of the limitations of the headlamp light sources available for study: Tungsten-halogen bulbs have a high CRI, a continuous SPD, and a relatively low CCT. HIDs have a low CRI, a discontinuous SPD, and a relatively high CCT. This is to some degree an implementational limitation, not a conceptual one, and in my opinion it is likely to be found, eventually, that a blue-rich SPD can cause glare problems but a high CCT can potentially improve seeing performance. That is going to be a tricky balance to optimise, for high CCT to a significant degree goes along with blue-rich SPD. But we're now seeing LEDs that have a higher CCT than HID headlamp bulbs, but without a proportionately higher blue spike. It will be interesting to see what shakes out of this. The marketeers may have to find another tactic, having already painted themselves into a corner using blue paint: up to now, the bogus claim of "whiter" headlamp light has been used to refer to light that is in fact bluer. When it becomes possible to provide headlamp light that is of higher CRI and higher CCT rather than just higher in blue content, that light will in a more real sense be "whiter" than HID headlamp light...but what are they going to call it...?

Originally Posted by Hilldweller

They're still blue-tinted and filtering out usable light; no filter adds light. It can only take some away.
In this case, it's taking away the good light that your eyes use to see better with.
And their reported "temperature" is fairly misleading.

Info:

Originally Posted by Hilldweller

They're still blue-tinted and filtering out usable light; no filter adds light. It can only take some away.
In this case, it's taking away the good light that your eyes use to see better with.
And their reported "temperature" is fairly misleading.

Info:

Originally Posted by D Stern

US, Canadian, European and Japanese regulations all call for "white" light. There is no one specific light color that is defined as "white" light; rather, there is a large range of output spectra that are considered "white", and the "white" light is permitted to exhibit visible tints of blue, yellow, green, orange or red. Various regulatory bodies are considering narrowing the "white" standard so that it is less permissive of blue tinting. Such has been the spread of blue headlamp bulbs that many police agencies have purchased in-field beam color testers—they use these on headlamps that look too blue to be legally considered "white".

Many motorists have been confused by marketing claims for the blue bulbs, which falsely and incorrectly equate the blue bulbs' performance with the very expensive arc-discharge ("Xenon") headlamps found on top-line luxury cars. They have been led to believe that by replacing their car's headlamp bulbs with the blue-coated bulbs, their headlamps' performance will be increased. In fact, quite the opposite is true; their headlamps' performance is decreased by the use of blue bulbs.

There is psychology at work in the marketplace, as well. Many of these blue bulbs are sold at very high prices in extremely attractive packaging. It is well known to marketers that the motorist who pays $35 or $45 or even $85 for a set of "special high performance" bulbs will probably perceive a performance improvement even if there is actually none.

Some motorists believe that the blue light makes their car look "cool". This would fall into the same category as the dark plastic headlamp and taillamp covers that are snapped-up by certain drivers for their appearance "enhancement" value, despite the fact that these covers, like the blue bulbs, are illegal and dangerous.

White light is made up of every color of light mixed together. But the colors are not all present in equal amounts. The output spectrum of filament bulbs, including halogen headlamp bulbs, includes a great deal of red, orange, yellow and green light, but very little blue or violet light. Blue bulbs have colored glass (or a filter coating applied to clear glass) that allows only the blue light through the filter — this is why the bulbs appear blue. Because very little blue light is produced by a halogen bulb in the first place, it is only this very small amount — a tiny fraction of the total amount of light produced by a halogen bulb filament — that ever reaches the road.

Blue and violet are the shortest wavelength/highest frequency colors of visible light, and, as such, they scatter the most readily. This is why the sky is blue rather than any other color from the sun's white output spectrum. Blue light doesn't just scatter most readily in the sky, but also in the eye. To observe this effect, try this informal experiment: Next time you see a dark blue storefront sign or a row of blue airport runway landing lights after dark, notice how blurry the edges of the sign or landing light appears compared to adjacent lights or signs of different colors. Decades ago, hot rodders would install "blue dots" in their cars' taillamps. These small bits of blue glass cause the taillamps to appear not red with a blue dot in the center, but rather pinkish-purple, because the observer's eye easily focuses on the red but has trouble with the blue, which remains out of focus and appears to tint the entire area of the red light.

suppose we want to add a filter to the glass that makes the light look bluer/colder. How does it do that? Well, there's no such thing as a filter that adds light into the beam passing through it; filters can only suppress light, not add it. So if we can't add green-blue-violet light, then the only way to get the light to look colder is to suppress green-blue-violet's opposites, which are red-orange-yellow. If we want the light to look, let's say, 20% colder, we suppress red-orange-yellow by 20%. Looking up above, we see that we've got a total of 750 lumens' worth of red, orange and yellow. So, cutting this by 20% leaves 600 lumens, plus essentially all of the bulb's original green-blue-violet output of 250 lumens, so we've now got a bulb that produces light that looks 20% colder and produces 850 lumens.

850 lumens happens to be the minimum legal output for a 9006. Unless we're craven marketeers who don't care about compliance or performance, we can't produce a bulb that produces only the bare minimum of light, because 50% of production will be 849 lumens or less. So, we have to put in a high-luminance filament to try to counteract some of the filtering losses. BUT we still have to come in under the max-allowable-wattage spec in DOT or ECE regulations.

So, let's say we build our 9006 with a super-duper filament that produces 1200 lumens. That's too much for a 9006, but we're going to take away some of those lumens with our colored filter (blue glass). This 1200-lumen filament produces, let's say, 300 lumens red, 300 lumens orange, 300 lumens yellow, 210 lumens green, 60 lumens blue and 30 lumens violet. Now we put that same blue glass over it, which suppresses red-orange-yellow by 20%. Now we've got 720 lumens' worth of red-orange-yellow after filtration, plus 300 lumens' worth of green-blue-violet. That gives us a 910-lumen bulb, which is enough above the 850-lumen legal "floor" that we can run the bulb and even if some filaments only produce 1150 lumens instead of 1200, we're still legally OK. Of course, we still only have 910 lumens instead of 1000, and our 1200-lumen filament is going to have a significantly shorter life than a 1000-lumen filament, but we've got our colder/bluer light appearance in a legal bulb.