Re: [doc] H4 bulbs on the D...

[Nick Tomlinson <nickandkathryntomlinson@xxxxxxxxxxx>]

We all have perceptions which is why Science tries and quantifies the things around us.
 
candela (cd)
The SI base unit for measuring the luminous intensity of light. Candela is the Latin word for "candle." The candela is defined as the luminous intensity, in a given direction, of a source that emits monochromatic radiation of frequency 540 x 1012 hertz and that has a radiant intensity in that direction of 1/683 watt per steradian. 
lumen (lm) 
The SI derived unit for measuring the luminous flux of light being produced by a light source or received by a surface. The luminous intensity of a light source is measured in candela. One lumen represents the total flux of light emitted, equal to the intensity in candela multiplied by the solid angle in steradians (1/(4·pi) of a sphere) into which the light is emitted. Thus the total flux of a one-candela light, if the light is emitted uniformly in all directions, is 4·pi lumen. 

I said it was complicated.
 
Right.....back to Deloreans, this isn't a boring physics newsgroup.
 
NickT.

Martin Gutkowski <martin@xxxxxxxxxxxxxx> wrote:

My point was that a 90/100W bulb will not be "nearly twice as bright" as 
a 55/60W bulb. At the end of the day, there are numerous cars out there 
running around on a single pair of H4's. The DeLorean has 2 pairs of 60W 
bulbs at high-beam and with quality lenses, kicks out a thoroughly 
impressive beam (when properly adjusted). It's certainly easier to drive 
my D at night than my Xantia.

Have a read of:

http://www.danielsternlighting.com/tech/bulbs/bulbs.html

Quote:

"Brightness" is like "Loudness". It's a subjective perception. Is 
Metallica " louder " than Bach? Most people would say so. That's why 
audiologists use an objective measurement, Sound Pressure Level, rather 
than subjective quantities like "volume" and "loudness". And so it is in 
the science of light. "Bright" and "Dim" are subjective perceptions. 
Intensity, measured in any of several precisely-defined and scientific 
ways, is the only real way to gauge or compare output of a light source 
or performance of a lamp equipped with a light source.

...he uses Lumens in his comparisons.

Martin


Nick Tomlinson wrote:

> I presume you mean "to double the bright intensity, the power of the 
> pulb has to be quadrupled (using the current lamp technology)"
>
> This can only regarded as a rule of thumb as the light intensity 
> cannot be determined by the power consumption. Power is defined as the 
> rate of energy consumption by an electrical device when it is in 
> operation.
>
> The SI Unit of Power is a Watt.
> The SI Intensity of Light is a 'Candela' (and is v complicated and 
> historical)
>
> Don't mean to be picky.
>
> In a nutshell JohnT Tien, due to the power consumption of the bulbs, 
> it is recommended that you don't use them UNLESS you add a relay 
> circuit and use heavier duty cable sufficient for the current of the 
> new bulbs but then again, do you really want melted headlamps & 
> eyebrow bumpers. Why not use the different gas ones like Xenon/ Neon etc..
>
> NickT





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