C.P. versus Lumens
I snitched this commentary from an internet board. The discussion centers on flashlights, but the discussion is relevant --
"There is no conversion or direct comparison between Lumens and candlepower. Candlepower is the measure of the brightest spot in the light beam. However this can vary depending on the focus of the beam, and the distance it is measured. No manufacturer lists the distance at which they measure the cp rating. Also they don't state the size of the hot spot they are measuring. It could only be a 1 inch bright spot in the edge of the beam. Lumens is the measurement of the total light output of a bulb, but not it's brightness. Most 60 watt incandescent light bulbs are rated at 800 lumens. This is more than even the brightest SureFire light, but compare the brightness of even the dimmest SureFire light to a desk lamp and the SureFire will be much brighter. Candlepower also changes by the focus of the beam, and the size of the reflector."
Hope this helps. The point, I suppose, is that the manufacturer's ratings of a light's output are relative at best, and not absolute measures to be compared between brands or between dissimilar units by the same manufacturer. Still, if candlepower relates to a bright spot in a beam pattern, that would tend to explain why spot lights have higher C.P. ratings than spread beam lights such as fogs or floods. Or, if comparing similar units and one has a lumen rating of 2,600 and another just like it but with a different bulb (i.e., 10,000K HID versus 4,250K HID), I would go with the one with the higher lumen rating simply because it puts out more actual light (not to mention the color shift problems with high heat HID's).