[MikeK]

Originally Posted by old31

The 32/50 is a great bulb and provide enough light for night time driving.

I have compared the 32/50's to the halogens and like them better. Cheaper and run way cooler and provide the same light.

Originally Posted by Y-Blockhead

Except you can't really compare the two. Candlepower is a measure of the brightest part of the beam of a headlight whereas lumens is a measure of the total amount of light put out by a headlight. Why can't they just make thing easy?

Measuring light has been a game of liar's poker since man first used fire!

You may have heard some of these terms: Lux, Lumens, Candlepower. Less known terms: Circular candlepower, Candela, Isotropic lumens. They are all units of different properties and thus cannot be directly converted mathematically like you can convert inches to centimeters.

The earliest light unit, the 'candle' was replaced with 'circular candlepower', usually incorrectly listed by bulb manufacturers as just 'candlepower'. WRONG!

Since no two candles are alike, the only true measure of visible photon production stems from photographic development and WWII research. In 1948 this method was officially dubbed 'Candela'. Today only scientific and technical light sources are rated in candela.

Modern lighting is usually rated in 'lumens' which is actually a wavelength biased measure of 'flux intensity'. Of note here, the term 'Lux' is derived from 'flux intensity'. Lumens may be directional and the number will change with spread concentration while the source is constant in 'candela'. The mix of wavelengths in white light, often weight averaged to a color temperature number in degrees Kelvin (K) affects computation of 'Lumens".

The same photon flux density from two sources, one red light, one green light, will exhibit lumen rating bias. The green source will have a higher lumen number despite equal photon flux densities.

Isotropic lumens (isotropic = nondirectional) are an attempt to quantify a light source in a manner similar to circular candlepower or candela but with some human eye response wavelength bias.

Keeping in mind it is inherently impossible to directly convert any of these units to each other, or to units of work or power such as Watts, I offer up the following numbers based on conditional and debatable algorithmic assumptions:

• 35W halogen ~ 649 lumens
• 32/50cp bulb = 29/45 watts (measured) ~ 470/729 lumens
• (the above are for halogens @ 7.2V, original 32/50cp @ 7.1V

Now, getting all that down the road into a usable beam shape without blinding oncoming traffic is a whole 'nother can of worms. Skew caps, beam linearity, reflective and transmissive coefficients would all come into that discussion.