Notice the pattern of the lights in Figure 2. They are carefully arranged to get maximum intensity in the area where paintable surfaces are located. In addition, the lights are only 7-8 feet above the fuselage at this point and lighting is extremely good. The large number of lights is also arranged to cast light onto the floor in strategic locations to allow for reflectivity to the underside of the fuselage and wings.
Sidewall lighting further augments the reflected lighting to give a highly visible surface at any point on the airplane. This helps the painter to eliminate skippers, runs and dust and dirt inclusions. More importantly, areas where corrosion would originate are found and repaired.