Convoy S21D w/ legendary Nichia 219b. Review & comparison w/ Nichia 519a, B35AM, FFL351A Rosy & "tint-snob" LEDs. (Summary & measurements on P. 1) LATEST: Firefly E07X with VERY rosy 351A LED and Lume1 Driver.👍

LED Flashlights – General Info 21700 Flashlights
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Well, in that case you’d want a weighted harmonic mean. Found an online calculator: Online Weighted Harmonic Mean Calculator

Lets throw out an example and use 2700/5700 with 2700 at weight 1 and 5700 at weight 1.3 (i.e. 30% more output than 2700)

Weighted harmonic mean = 3843K