Join Date: Sep 2005
Bikes: Windsor Fens, Giant Seek 0 (2014, Alfine 8 + discs)
There's no direct relationship, they don't really measure the same thing (well, they're both related to brightness but they're measured in different enough ways that it's almost impossible to directly convert).
My basic rule is that, these days, if they list the brightness in candlepower, it means it's not very bright. All the actually bright systems use lumens.
Work: the 8 hours that separates bike rides.