Okay, lets examine your 'facts'
Originally Posted by
cyccommute
Let's assume that a car light has an area of about the same as a 2"x4" reflector. It doesn't and a 2"x4" reflector is larger than anything I've ever seen incorporated into a light but, for sake of discussion, let's assume they are equal.
Sorry, but the source itself isn't the size of the light, the reflector is... And as a Tim Allen type yourself you should realize the reflector on a pair of car lights is quite a bit larger
Originally Posted by
cyccommute
Let's assume that a car light has an area of about the same as a 2"x4" reflector. It doesn't and a 2"x4" reflector is larger than anything I've ever seen incorporated into a light but, for sake of discussion, let's assume they are equal. A car lamp puts out 1500 lm and a 2"x4" are is 0.005 sq meters. The lux, a measure of lumens per unit area, of the car lamp is 300,000 lux at the lamp face. Using the inverse square rule, the intensity of the light at 25 feet is 480 lux or 480 lm/sq m. The amount of light hitting the reflector is 2.4lm. If the reflector is hit dead on and we assume that 100% of the light that hits the reflector is sent back...not a valid assumption but I'll give it to you anyway...the amount of light that gets back to the observer is 0.0038 lm. Even if the reflector was a square meter in area, the total lux getting back to the observer is only 0.76.
Now to the bike light. A bike light has an aperture of about 1" or about 0.0005 sq m. Let's look at two different light outputs, 300 lumen and 600 lumen. At 300 lumens, the lux at the light is 600,000 lux. At 600 lm, the lux at the light is 1.2 million lux. Again applying the inverse square law, an observer at 25 feet would see 1920 lux. Last time I checked, 0.79 lux is less intense than 1920 lux.
The values above for the light returned would be even lower if you hit the reflector at any angle other then dead on.
So you see, your statement that "NO BICYCLE LIGHT overwhelms the light from a reflector is not accurate. Not accurate at all.
Care to do those 'calculations' for daytime? Or for the lux of a bicycle's light after applying that inverse square law? No, I guess not...
You clearly didn't read my entire statement; "And NO BICYCLE LIGHT overwhelms the light from reflectors,
especially in the day time" Nor are you considering that the front and rear reflectors on a bike are also supplemented by the bicycles lights (dyno in my case)... not instead of such lights in my statement... I know you didn't bother to let what I actually wrote conflict with your beliefs;
Originally Posted by
cyccommute
I deplore passive reflectors. I don't even see the reflectors as augmentation of the active lights but only a nuisance that I have to have to be legal.
And of course your numbers are based upon halogen bulbs from 1983 specs, not modern HID or LED bulbs (which are also being implemented in cars as well as bikes, and with far more power available). And you have not addressed car's high beams (which are the most likely to be encountered by cyclists who aren't being seen, ie in a dark environment at night)... Those highbeam produce between 3 and 4 times as much light output...
In short your 'analysis' is what is typically called 'cooking the books'...