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submitted 1 week ago by xkcdbot@lemmy.world to c/xkcd@lemmy.world

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Title text:

I'm trying to buy a gravitational lens for my camera, but I can't tell if the manufacturers are listing comoving focal length or proper focal length.

Transcript:

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[–] DarkCloud@lemmy.world 21 points 1 week ago (3 children)

Narcissian... Also known as a mirror.

[–] Akasazh@lemmy.world 5 points 1 week ago

Or a pond

[–] nialv7@lemmy.world 2 points 1 week ago

funny mirror

[–] psoul@lemmy.world 2 points 1 week ago

Also known as the cabinet of curiosities, the door to the world that should not be seen, Medusa’s bane.