This MacBook is still new to me, I am getting used to the brighter screen coming from a 2013 15" Retina. This seems pretty bright! Anyway, I can be working on it and then after a while the screen colour will adjust, I understand this, but it is happening when no other lighting has changed anywhere in the room. Is True Tone slow to respond. When I turn it off the screen is a warmer colour. Is this right?