A common misperception contributing to the proliferation of ineffective and inefficient lighting is that more light equals higher quality light. Lighting-level requirements have evolved with the changes in our workplaces and our knowledge of visual science. The Illuminating Engineering Society of North America (IESNA) has developed consensus-based guidelines to select appropriate luminance levels for hundreds of indoor and outdoor activities. These recommendations are starting points, suggesting a range of values based on design issues, locations, and tasks. Listed below are several design issues outlined by IESNA:

• Appearance of Space and Luminaires
• Color Appearance (and Color Contrast)
• Daylighting Integration and Control
• Direct Glare
• Flicker (and Strobe)
• Light Distribution on Surfaces
• Light Distribution on Task Plane (Uniformity)
• Luminances of Room Surfaces
• Modeling of Faces and Objects
• Point(s) of Interest
• Reflected Glare
• Shadows
• Source/Task/Eye Geometry
• Sparkle/Desirable Reflected Highlights
• Surface Characteristics
• System Control and Flexibility

Lighting levels should be customized through the use of supplemental task lighting in areas requiring higher localized levels. Target lighting levels should be the sum of the ambient and task lighting levels. This task and ambient lighting design approach creates flexibility to accommodate individual tasks or worker requirements, creates visual interest, and can save considerable energy in comparison to a uniform ambient level approach.