Light Research

["Al Powell" <APOWELL@agcom.tamu.edu>]

> From: quk@sievers.com (Phil Payne)
Phil suggests using light meters in incident mode to compare light.

I think this would work very well.  Here is the test situation I 
would suggest: have two sets of lamps.  One set 55/60 standard 
wattages, one set with whatever flamethrowers are handy (If two 
people do the same test, both sets of hi-watts should be same wattages.)

Dark night, as little light from moon, etc. as possible.

Compare light readings at 100 yards and 200 yards from vehicle 
(if you want to get fancy, do botha  direct reading and one of light 
reflected from a white card 1 meter square, which is the 
specification for measuring both lux and lumens, if I recall 
correctly (harumph, harumph...)

Measure light at the following positions with NORMAL and HI-WATT 
lamps in place:

1)  Center of driving lane
2)  Center of oncoming lane (yes, I know it's different in US and GB)
3)  10-ft off road on driving side of road

This would yield illumination differences and give us an idea how far 
down the road those differences might be realized.

Phil said:

> Checking the quad Euros in the Coupe GT (55 watts) the peak reading I can get 
> on low beam is 17 on the Lunasix scale, or around 11000 lux.  On the quattro 
> (_real_ Euros with 100w low beams) I get around 18 1/3, or around 30000 lux.  
> Full scale on the Lunasix is 22 (350000 lux) so it has the range required for 
> the job.  The question is whether Eric and anyone else interested in 
> measurements can find one ...

Interesting.  Not quite 2x the wattage yielded not quite 3x the 
illumination!

What was the position relative to the car, and the distance at which 
the reading was taken, Phil??  The setup I suggest would allow one to 
determine both light output and whether light output is higher 
farther down the road.  


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Al Powell, Ph.D.                 Voice:  409/845-2807
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