Autolamps

It’s a huge subject but I will try and keep it as simple as I can because we keep getting asked.

Firstly colour temperature is purely the X Y co-ordinate on the black body curve. It has nothing to do with brightness or lightoutput it is simply a colour point. On all image manipulation software like Photo shop, Corel draw you have colours and that colour has a co-ordinate usually an RGB mix (Red Green Blue). This is EXACTLY how the colour co-ordinate is based for Colorimetry for lamps. It is still a mix (as all light) of RGB but is expressed on the colorimetry graph as an X and Y co-ordinate and as such has a colour temperature rated at xxxxx degrees Kelvin.

Lumen spec on a light source and here on car lamps is measured in a photometric sphere and is the measurement of the TOTAL light output from that lamp. This is where the R37 and DOT specs are drawn up.

However the important performance aspect on a headlight beam is its distribution and luminance. Luminance is a figure taken at the filament and is expressed as CD/M2. It is in simplistic terms how bright is that single spot on the filament as opposed to how much light is the whole filament giving out. Why is this important? Well your reflector and lens collect 10000's of images of the filament and distribute them up the road. You beam is infact made up of 10000 of images of your filament. The art of the headlamp designer (now done on a computer) is how to distribute these images. If you want to try and prove this park up in a dark garage and turn all the lights off except your headlight. Cover the side you don’t need and park up a few feet from the wall. Now take a piece of card big enough to cover your headlight and make a nail size hole in it. You will now see with some movement a single image of a filament on your garage wall. Move the card around over the headlamp lens and the filament will move. What infact is happening is that at each point on the lens you have a different image of the filament.

Now if you take that filament and reduce its size and burn it harder it becomes 'brighter' expressed as a higher CD/M2. If each of the filament images on the road in your beam are now brighter you have better headlamp performance. This is the reason why you have the Vision plus at 50% better performance while only being rated at the same wattages as the standard lamps

mmmmmm a tad long but I hope this helps

Nick

Dave T-S

Nick

Or in other words the bottom line is; the filament is thinner, creates more resistance, burns brighter thus gives out more light!

That's what most people on here want to know

[Edited by Dave T-S - 2/16/2002 12:32:44 PM]

Autolamps

No not exactly

What you would end up with this approach is the lamps failing through shock or vibration due to the thinner filament. If this was the approach all lamp manufacturers would just simply reduce the cross section of the tungsten.

Nick

Dave T-S

Well yes.......a bulb is a resistor, nothing else.

There is basically only one reason why "brighter" bulbs are so - they have a thinner filament which causes more resistance, and thus runs hotter, and therefore brighter.

Xenon gas allows the filament to run hotter than most other bulb envelope gases without vapourising itself.

A bulb lives in an unhappy medium where its very existence is to run on the edge of self destructing and the filament is permanently trying to vapourise itself, with only the gas that surrounds it preventing it.

You could have a 500w equivalent bulb but it would only last seconds or minutes before it self destructed - there is always a trade off between ultimate lumens output and bulb life.

As we both know, common bulb killers are:

Bad connections.
Voltage spikes.
Too high voltage.
Vibration.
Thermal shock.
Excess bulb temperature.

Poor old bulb;

But i'm not trying to teach my granny to suck eggs.....






[Edited by Dave T-S - 2/16/2002 7:42:52 PM]

Autolamps

Good discussion, not sure if anyone else will agree?

For the purpose of this discussion as it started on Vision plus we will assume its a Philips product and a halogen lamp.
Bad connections.
Agreed but limited impact on the life of the lamp. All the lamps are designed around a switching cycle.
Voltage spikes.
Agreed dependent on their peak and duration. 37000 early 90's Jags cant all be wrong!
Too high voltage.
The killer of all car lamps without question by this equation
http://www.autolamps-online.com/howwhy/voltlifecentre.htm
Vibration.
Agreed again depedent on peak and frequency.
Thermal shock.
NOT AN ISSUE. The lamps are internally cleaned , primed and then sealed when the glass is heated to white hot and then pinched closed. While still white hot the envelope is then super cooled using liquid gas taking the glass temperature from approx +1000 deg to -250 in a split second. Part of the show demonstration is to burn the lamp to max operating temperature and then immerse it underwater, the lamp continues to burn. This is due to the charactersitics of the quartz glass used in the Philips lamps. Everyone else uses hard glass which would explode
Excess bulb temperature.
Depends. Ambient temperature is not an issue but overheating the filament as you say will kill the lamp.

Its good to find somebody on these forums that knows what they are talking about. Enjoy the rest of your weekend

from your granny!!

Dave T-S

Nick

Five out of six aint bad!

Surprised at the thermal shock issue. That is one *serious* test!

Never mind the granny bit, i'm old enough to be someone's grandad at 47, been putting auxiliary lamps on my cars since 1971

It was probably after putting about my 5000th H2 bulb in a Cibie lamp (now THAT is a horrible piece of design) some years ago I got interested as to why they lasted no time.....

Autolamps

Its a small world

I was involved with the development of the Oscar Plus when I worked in the Cibie competition department 20 plus years ago. Should I say sorry now ?

It is and was a great lamp but I agree with the H2 issue. The H2 was developed by Philips in Chartres , France specifically for Cibie. The H1 was a Philips innovation in 1968 but the French didnt want to use it as it was developed in Germany. The H2 was their version of the H1 with a different base.

cheers

ChrisB

A very interesting read - cheers guys

Hoppy

For a slightly different take on this discussion...

Output and lumens are all very well, but with car headlights where the light output is very low compared to daylight, it is important to take into consideration the light sensitivity of human eyes and try to optimise your lights with them.

And they are significantly more sensitive to yellow/green than to blue (the colour of road safety workers' jackets). The hotter you run bulbs, not only are they more likely to blow, but they output more blue light which doesn't help you see any better.

Furthermore, blue light refracts in the atmosphere (that's why sunsets are red) and in fog, blue lights can be posititvely dazzling - more yellow is what you want. (Sorry to be desparetely unfashionable here.)

Much better therefore to run higher wattage bulbs cooler (than lower wattage bulbs, with narrow filaments, hotter) that put out more of the light that you can actually see by.

And if we're getting scientific here, please let's not talk about "degrees Kelvin". The plural is Kelvins.

Richard.

PS Why can you see so well under such dim yellow (sodium) street lights (albeit in monochrome)? Why do the French use yellow headlights? Maybe because they want to see where they're going, rather than looking trendy

Richard.

Dave T-S

Nick
Cibie are great lamps - or they would be if they ran them on H3 bulbs LOL

Hoppy
It is no longer a mandatory requirement to run yellow lamps in France - so they must have gone all trendy

Mungo

I'm glad someone got in there and corrected the "degrees Kelvin" faux-pas!!
Surely reflector and lens design are as important as the bulb design? I'm sure that this is what lets Scoobys down more than anything when it comes to the headlights. I'm jealous just looking at the pool of light (on dipped beam) in front of other cars on the m'way. It's generally much brighter and much longer than mine (phnar phnar). I guess their lens focuses it much better on the tarmac.... (and I've got the Visionplus bulbs)

Autolamps

If we want to be perfect and factually correct the measurement is on an absolute scale and it is 'Kelvin' i.e. 4200 Kelvin. Kelvin is the scale as per Fahrenheit for temperature. It is not 32 degree Fahrenheits as in plural. Kelvin is only ever used in the singular and in day-to-day lighting terminology is often referred to as degrees Kelvin.

Sorry for any confusion

Mungo

Exactly.
Confusion excused!!!

carl

First of all, it is kelvin and not Kelvin -- SI units are not proper nouns. I know the bloke was called Lord Kelvin, but it's not Amperes either.

Also, it is kelvins as it is an SI unit (that of absolute thermodynamic temperature) so the same rules must apply as that for amperes, volts, lumens, etc.

See http://physics.nist.gov/Pubs/SP811/sec09.html#9.1

Also the only way to make the filament 'burn hotter' for a given input voltage is to change the resistance by use of a different material or making the filament thinner. I was going to say 'or longer' as resistance obviously increases with length, but the brightness of a point on the filament is a function of its resistance per unit length (assuming infinitely thin filament). IIRC this is called resistivity.

Mungo -- also try looking out of the side windows when driving down a hedge-lined lane, and see how much light is wasted out of the sides. If you compare the Scoob's headlight units against a BMW or Merc's, you'll find those on the Kraut-wagens are much deeper.

Also, the difference between the actual temperature of a tungsten filament and its colour temperature (which is the equivalent temperature of a black-body radiator) shows you how dissimilar the tungsten filament is to a black body radiator (for which, FYI, you only need the X-coordinate as the curve is defined). It's kind of like the difference between an '8 ohm' loudspeaker and an 8 ohm load.

BTW -- just looked at the Autolamps site. Very informative. H4 HID prices look pretty cheap, too.

taz

Sorry to hijack your thread but after looking at your website (very interetsing) you can get conversion kits for existing cars. I have admired the hid headlights for a couple of years now on the likes of Mercedes and Audi's "S" range being the most striking I have tried to get a bulb to replicate this but have spent a lot of watsed money to get no results. Are the kits on the website

1) Reliable and warrantied
2) Worth the money
3) The same as the Audi ones
4) Easy to fit to different kinds of cars

I am very interested as most cars have chocolate lighting and I am envious of the Audi ones

Please enlighten me :d :d

Graham

Autolamps

Hi Taz

I dont want to hijack the forum with specifics but I am happy to answer your questions. Please contact me directly on autolamps-online@autolamps-online.com and I will do what I can to help

Nick