What is the difference between a photograph and a eyewitness to an event and a painting depicting the same event?

An photograph is arguably the best way of having evidence for something, as it is a real image of something. An eyewitness may be true because it was someone that was there but that person might not remember things in full detail. A painting is very subjective because of the different styles artists paint, and also people are moving during the event so it is very hard to get a still picture to paint.