The VCP index provides an indication of the percentage of people in a given space that would find the glare from a fixture to be acceptable. A minimum VCP of 70 is recommended for commercial interiors, while luminaires with VCPs exceeding 80 are recommended in computer areas. The uniformity of illuminance is a quality issue that addresses how evenly light spreads over a task area. Although a room's average illuminance may be appropriate, two factors may compromise uniformity. The ability to see colors properly is another aspect of lighting quality.
Light sources vary in their ability to accurately reflect the true colors of people and objects.
A higher CRI means better color rendering, or less color shift. Under higher CRI sources, surface colors appear brighter, improving the aesthetics of the space. Sometimes, higher CRI sources create the illusion of higher illuminance levels. The CRI values for selected light sources are tabulated with other lamp data in Exhibit 3.