22 August 2006
Use direct light only in limited amounts for task and accent light. Refer to
specific applications in Chapter 6, "Interior Applications".
For exterior applications, use fully shielded luminaires (see exterior
luminaires in Chapter 5, "Lighting Equipment" and Chapter 7, "Exterior
UNIFORMITY. Lighting level or illuminance uniformity is important on work
surfaces where sustained tasks are performed as well as on wall and ceiling surfaces
that make up a significant portion of the field of view. Poor uniformity can cause
adaptation problems. It is very important to prevent "spotty" lighting especially in interior
areas where people are working, and exterior areas where safety and security are
Flicker or strobing of luminaires can cause annoyance as well as headaches
and fatigue. This may be caused by fluorescent ballasts near the end of life or
placement of luminaires in relation to ceiling fans. If ceiling fans are required in a
space, position the luminaires so that they are suspended below the level of the fans.
Figure 2-5. Uniform ceiling brightness.
Figure 2-6. Uniform illuminance.
Requirements for appropriate uniformity:
Follow IESNA uniformity criteria for specific areas unless superseded by
other UFC criteria. Refer to specific application requirements in Chapters
6 and 7, "Interior and Exterior Applications" and Chapter 10 of the Lighting
Considerations for appropriate uniformity:
In office areas, uniformity should not exceed 5:1 in immediate work
surrounds, not including accent lighting. Also, refer to Chapter 6, "Interior
Exterior uniformity should not exceed 10:1 along areas of use including
roadways, walkways, and parking areas. Refer to specific application in