Back in the film days, there was a lens speed race.Every manufacturer was intent on coming up with faster lenses...

Back in the film days, there was a lens speed race.Every manufacturer was intent on coming up with faster lenses ("f-stop" rating).Now days, as astronomical EI (ASA) common pace, lens speed is much less of an important factor.

But, I always wondered: Is there a top speed, a theoretical limit?

See the video...
https://www.youtube.com/watch?time_continue=360&v=84ZXfviMBFE