To me it's rather unclear what problem you're seeing. The mouse can only move at a certain speed over your window. If it's a 1:1 mapping then it would just move as fast as you see your mouse move, I don't understand why you think this is too fast, nor what it has to do with the view.
Maybe post some code and explain what you want to achieve, so we can understand the problem.
Personally, I'd recommend using events to track mouse position, instead of using sf::Mouse::getPosition()