Headlamp bulbs.

I seem to get around quite happily with sealed beams! Especialy since I cleaned up the gearbox-chassis earth strap - what a difference! I'm not noted for driving cautiously....

Richard

On or around Sat, 21 Feb 2004 00:01:08 +0000, richard.watson enlightened us thusly:

there's a lot of variation in night vision from person to person. Mine isn't very good, hence I want decent lights. Sealed beams are still 60W main beam though, just that the light's a bit yellower.

Avoid these - useless. If you want decent replacement bulbs then get some Phillips Vision Plus.

Did you read the garbage on the auction itself?

What is the 6000K?

This is the temperature that the bulbs heat up to. Don't be fooled by xenon bulbs that only contain 3800K-4000K these are not bright. Our bulbs heat up to 6000K. Lighting up your whole road.

So, what's that, 5727 degrees celsius, or somewhere around the melting point of most things? These bulbs must put light on the road by turning the reflectors into plasma.

P.

On or around Sat, 21 Feb 2004 18:06:22 +0000, "Paul S. Brown" enlightened us thusly:

yeah, I was amused by that.

Contrary to all the learned advice here so far, I have a set of these very bulbs in my bike and they made a vast improvement. As a result, I have bought a set of H7's for the 130 to fit into the crystal sealed-beam units.

Malcolm.

On or around Sat, 21 Feb 2004 22:13:15 +0000 (UTC), snipped-for-privacy@cix.compulink.co.uk enlightened us thusly:

horses for courses. what wattage are they? the advert doesn't admit to that. I don't doubt that by upping the wattage, you can overcome the inherent inefficiency of the blue filtering, and get as much light as you'd ordinarily get from a 60W bulb, or even more. But you can do that anyway by running 100/80W bulbs, but they're not "100% street legal", or not in the UK anyway.

I've seen some of the very-blue ones before advertised which were 130/90W ISTR, but I don't know if they were the same as these. I've also followed a vehicle with blue headlamps, and although the light was blue-white, there was sod-all of it, compared to my humble 60W normal halogens...

In article , Paul S. Brown writes

Presumably they achieve an equivalent colour temperature of 6000K by a blue filter. If those things are halogens the filaments are around

3.5kK, glass envelope much lower (around 900K if memory serves).

Regards,

Simonm. (probably not keeping up at the back, but hey, it's a Landy!)

Colour temperature is a somewhat theoretical measure, and the filtering isn't necessarily a well-matched correction. Another example are the blue-tinted bulbs used bu some artists to light their work area, which more-or-less match the desirable north-facing window.

I have an old book about photographic filters which deals with this sort of thing, though in terms I've not seen used elsewhere. It gets a bit dry and technical at times, though it's a translation of a German book and there might be a little cultural bias.

The thing is that a particular filter will not give a constant shift in colour temperature. The difference between 5000K and 6000K doesn't look the same as the difference between 2000K and 3000K. What this book used as a measure was the Mired -- million reciprocal degrees. So 6000K is

166 Mireds. And using that measurement, the filters have a constant numeric value.

Which, 20 years ago, I though was neat, and useful, and I stuck Mired labels on the cases for all my colour-correction filters.

Unless you're getting specialised colour film, it'll be balanced for daylight, and even the tungsten-balanced film is for a higher colour temperature than ordinary domestic bulbs. Our eyes and brains will compensate for this: film doesn't. Digital photography, and video, can adjust for the white balance in the camera.

The deep blue filters you need to get the proper colour balance for daylight film do horrible things to the effective film speed.

Fluorescent tubes, incidentally, have different colour problems.

Anyway, while that's more than anyone probably wanted to know, that blue tint in the bulb would probably need to stop 75% of the light to get the right colour for 6000K. And your eyes almost certainly will not see the difference in colour. But it wouldn't surprise me if film makers were to use such tinted bulbs to match the headlights in the scene with the lighting _of_ the scene.

In article , David G. Bell writes

I'm well aware of the behaviour of filters. I was referring to black body emissions and the sort of ad-hoc filtering used by lightbulb manufacturers ("make it a bit bluer"). I used to work in television, where colour temperature is a continuing issue (albeit less than in the past as quality standards have plummeted since the 'digital revolution').

Regarding film lighting: it's almost universally halogen cycle or HMI (discharge). Lamps are filtered, but tungsten-balanced stock (similar to the old "type A") is still used, at least for studio work. Colour temp correction is usually not applied to headlamps etc. simply because they are in shot and burn out anyway.

There's still a choice of camera stock available, with balance for temps from 2500K upwards (I believe there's even an element of customization possible for the really big productions, not usually available to stills photographers - see the Imax and Panavision technical sites, for example). Nowadays, practically nothing escapes digitizing, and much grading is done in the digital domain. It permits far more exotic colour and exposure corrections than before, and 'crossed curves' are rarely an issue.

Regards,

Simonm.