Opinion: Lumens should be an SI base unit
Disclaimer: I’m only an armchair metrologist. Experts, have mercy
In learning the definition of a candela (watts per steradian of visible light), I realized that lumens are simpler and easier to understand despite being a derived unit. They’re also widely used in the real world, unlike candela.
The original definition of a candela is the luminous intensity of a whale fat candle. If the entire point of a candle is to radiate in every direction, shouldn’t the base unit measure the total flux (light) the candle produces? Using lumen as a base unit is also simpler because its definition would equal the power of a light source weighted for human vision, and there’s no need to understand solid angle unless you need to use the (very niche) candela.
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 Andy Anderson, CC BY-SA 4.0 https://creativecommons.org/licenses/by-sa/4.0, via Wikimedia Commons
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Last modified: 10/26/2021