Art, Set Decoration & Lighting Departments covers three more of the most important people on the set. The Art Director deals with the Production Designer. This person designs and oversees construction of all sets, painting and outfitting of all sets.
The Set Decorator does the grass roots research of how the set should look. He purchases items for the set and sees that they are distributed appropriately.
The Gaffer is the head of all lighting and electrical systems on the set. Usually associated with lighting, he determines the electrical requirements for a set and sees that they are handled properly and safely.