A camera assistant is someone who assists the cinematographer in filming scenes. A first camera assistant is also known as 1st AC or a Focus Puller is the person who is most responsible for keeping the focus on the scene. They are the camera pullers and help in focusing on a particular angle or shot according to the cinematographer's direction. Focusing and following a script at a right angle with own judgmental knowledge is necessary for a camera assistant.
They need to be skilled at their work as re-shooting a scene is expensive and to get the right scene again. They are also responsible for all the camera equipment and its maintenance. They are the second in command after the Director of Photography on a film or TV show set. There are also second camera assistants known as Clapper Loaders who work on the camera equipment and how it is maintained.