Effect of White Walls on In-Plant Performance of Automotive Paint Inspectors

Charles Lloyd, Robert Strobel, and Peter Boyce

From a June 1996 technical report written for the Lighting Research Center, Troy, New York.


This report describes an evaluation of two forms of lighting for inspecting the paint finish on vehicles painted at the Twin Cities Paint Plant of the Ford Motor Company. One form of lighting has white wall board placed between regular arches of bare fluorescent lamps in industrial reflector luminaires forming the tunnel through which the vehicle bodies pass for inspection. The other form has the same arches of fluorescent lamps but the space between them is left open and is much darker than the white walls.

The evaluation involves measuring the number of defects repaired by Seek and Repair (S&R) workers while inspecting vehicles produced in the plant over four successive day shifts and informally asking the S&R workers which form of lighting they prefer.

The data collected demonstrate that:

  • The installation of the white wall board between the luminaires significantly reduces the ability of the S&R workers to find defects in the paint finish. This effect is consistent with the influence of the white walls on the contrast of topographical defects in paint.
  • The S&R workers prefer the sides of the facility with walls over the sides with no walls.

The reasons for that preference are unknown.

The results obtained are limited to small-area topographical defects of the type that occur when dirt is embedded in the paint. They are also limited to paint defects occurring on flat surfaces and by the small number of observers used. However, the results are sufficiently promising to recommend an attempt at validation with a larger set of participants who have recently purchased automobiles. Such an attempt would require the construction of a larger set of defect samples seen by a much larger and more representative sample of new vehicle buyers. It is also recommended that an instrument for measuring defect area and modulation, suitable for field use and based on the method reported here, be developed and tested. Finally, it is recommended a wider range of outdoor lighting conditions be used as part of the next evaluation.