The Gaffer is the lighting specialist on set, responsible for ensuring that all lighting is properly set up and functioning. They work with the director of photography (DP) to design and place lighting equipment, and they have a thorough understanding of lighting principles, such as color temperature and intensity. The gaffer must also be familiar with various types of lighting equipment and how to use them effectively. They must be able to work quickly and efficiently, as lighting can be time-consuming to set up.