There are so many different stadiums, times, games where the background behind the pitcher affects the ability to pick up the flight of the ball. Milwaukee is especially bad as there is this bright box on the back wall of the stadium. Anything coming out of the pitcher's hand up high is lost for just a nano-second against that box. Very distracting. Sometimes, in other stadiums, it looks like the ball is coming out of shadows...11am games.
All it takes is just a slight hitch in the lighting to really affect the ability for the batter to track the pitch.