50J is one of the indexes indicating the shock resistance.
It is shown that it is used by testing method based on IEC 60068-2-75(Test Eh: Hammer tests), 
it is set impact energy to 50 J(joules) and it can get through a house test to apply to the top of dome cover.

 

A Video of the impact test for camera is available at the following URL.
https://www.youtube.com/watch?v=AwxzeOS0tLU "Panasonic Vandal Resistant Camera Impact Test”