Magnifying The World’s Brightest Flashlight (200,000 Lumens)

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Flashlight I used: https://amzn.to/3Lj2fM3

Good summaries of Etendue:
https://www.mikewoodconsulting.com/articles/Protocol%20Winter%202012%20-%20Etendue.pdf
https://what-if.xkcd.com/145/