Like say if I were to review a movie could I use a screen shot or quotes from that movie and still monetize if I do not use many screen shots? Fair use seems kind of vague, and I am not exactly sure if I can or not. Like professors for example often write books based off of their views of non-fiction and publish them and make money while using quotes from those books or movies and I dont feel most professors were given permission, they just feel like doing research, giving theories or reviews on things and while most students that write papers are not doing it for profit, many professors are doing it for a living. So how does this translate to youtube, are there different rules since it is video and not a book?