|Even a professional high speed camera can't keep up with that.|
A professional high speed camera can do millions of frames per second and they are even working on frame rates running into billions.
With modern super sensitive CCDs such high frame rates are possible. It would not be possible with a conventional film camera.
I wouldn't worry too much about current. In fact you may need some current limiting resistors to avoid blowing the LED;s
When RS232 was common I had a LED tester witch plugged itnto the RS232 port in series with the cable. The LEDs flashed in accordance with the control and data signal passing through the connector, Red for Low. Green for High It had no adverse effect on the normal operation of the connection.