In a 1962 episode of the television series Rawhide, "The Devil and the Deep", trail boss Gil Favor and trail hand Rowdy Yates talk about looking forward to arriving in Abilene where they will sell the cattle they have been driving across the country and collect their wages. Rowdy says Abilene is the biggest little town in Kansas and he has no problem selecting company to spend his money with because, after all, "Only half the population is women, half of that is young, and half of that is pretty." That narrows it down significantly. It is the same process with bicycle lights.
There are a lot of brands because it is a big category in the relatively small bicycle industry. We have NiteRider, Olight, Planet Bike, Light & Motion, Blackburn, Cygolite, Knog, Portland Design Works, Skye, Sunlite, Delta, Nite Ize, Topeak, and Sigma. Did I miss any? Each brand has one or five good, better, and best options. In January Wirecutter published their 2020 bicycle light recommendations after claiming to have tested 90 lights over the last 6 years! If you care about putting the best lights on your bicycle, making that selection requires a process for narrowing it down.
The newest, brightest lights are rechargeable. so that eliminates at least half the population. Here are some other criteria:
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Sharon Kaminecki and others comment on adventures in bicycling and other stories