Can't help with CDG, but 50 minutes non-Schengen to Schengen at AMS is extremely tight. It's not the end of the world if you don't make it, though, as they will just put you on the next flight.

The problem with Schiphol is that they have not changed the Minimum Connecting Time since at least the late 1980s... when the airport was a lot smaller and when you did not have to go through Immigration or re-clear security. 1980s MCTs just aren't realistic in 2010!