Color Rendering Index(Cri). In 1964 the Cie Commission Internationale de l'Eclairage)officially adopted the IES procedure for rating lighting sources and developed the current standard by which light sources are rated for their color rendering properties. The CRI is a numerical value for the color comparison of one light source to that of a reference light source Color Preference Index(CPI). The CPI is determined by a similar procedure to that used for the CRI. The difference is that CPI recognizes the very real human ingredient of preference. This index is based on individual preference for the coloration of certain identifiable objects, such as complexions, meat, vegetables, fruits, and liege, to be slightly different than the colors of these objects in daylight. CPI indicates how a source will render color with respect to how we best appreciate and remember that color. Equivalent Sphere Illumination(ESI). ESI is a means of determining how well a lighting system will provide ask visibility in a given situation. ESI may be predicted for many points in a lighting system through the use of any of several available computer programs or measured in an installation with any of several different types Visual Comfort Probability(VCP). Discomfort glare is most often produced by direct glare from luminances that are excessively bright Discomfort glare can also be caused by reflected glare, which should not be confused with veiling reflections, which cause a reduction in visual performance rather than discomfort. VCP is based in terms of the percentage of people who will be expected to find the given lighting system acceptable when they are seated in the most undesirable location. Factors and remedies Quality of illumination pertains to the distribution of luminaires in the visual environment. The term is used in a positive sense and implies that all luminaires contribute favorably to visual performance. However, glare, diffusion, reflection, uniformity, color, luminance, and luminance ratio all have a significant effect on visibility and the ability to see easily, accurately, and quickly. Industrial installations of poor quality are easily recognized as uncomfortable and possibly hazardous. Some of the factors are discussed in more detail below. electric,it is defined as direct glare. To reduce direct glare, the following suggestions may De useful ght or Direct Glare. When glare is caused by the source of lighting within the field of view, whether dayl a. Decrease the brightness of light sources or lighting equipment, or both. b. Reduce the area of high luminance causing the glare condition C. Increase the angle between the glare source and the line of vision d. Increase the luminance of the area surrounding the glare source and against which it is seen. To reduce direct glare, luminaires should be mounted as far above the normal line of sight as possible and should be designed to limit both the luminance and the quality of light emitted in the 45-85 degree zone ecause such light may interfere with vision. This precaution includes the use of supplementary lighting equipment. There is such a wide divergence of tasks and environmental conditions that it may not be possible to recommend a degree of quality satisfactory to all needs. In production areas, luminaires within the normal ield of view should be shielded to at least 25 degrees from the horizontal, preferably to 45 degrees. Reflected Glare. Reflected glare is caused by the reflection of high-luminance light sources from shiny surfaces. In the manufacturing area, this may be a particularly serious problem where critical seeing is involved with highly polished sheet metal, vernier scales, and machined metal surfaces. There are several ways to minimize a. Use a light source of low luminance, consistent with the type of work in process and the surroundings. b. If the luminance of the light source cannot be reduced to a desirable level, it may be possible to orient the work so that reflections are not directed in the normal line of vision C. Increasing the level of illumination by increasing the number of sources will reduce the effect of reflected glare by reducing the proportion of illumination provided on the task by sources located in position reflections e 2000 by CRC Press LLC© 2000 by CRC Press LLC Color Rendering Index (CRI). In 1964 the CIE (Commission Internationale de l’Eclairage) officially adopted the IES procedure for rating lighting sources and developed the current standard by which light sources are rated for their color rendering properties. The CRI is a numerical value for the color comparison of one light source to that of a reference light source. Color Preference Index (CPI). The CPI is determined by a similar procedure to that used for the CRI. The difference is that CPI recognizes the very real human ingredient of preference. This index is based on individual preference for the coloration of certain identifiable objects, such as complexions, meat, vegetables, fruits, and foliage, to be slightly different than the colors of these objects in daylight. CPI indicates how a source will render color with respect to how we best appreciate and remember that color. Equivalent Sphere Illumination (ESI). ESI is a means of determining how well a lighting system will provide task visibility in a given situation. ESI may be predicted for many points in a lighting system through the use of any of several available computer programs or measured in an installation with any of several different types of meters. Visual Comfort Probability (VCP). Discomfort glare is most often produced by direct glare from luminances that are excessively bright. Discomfort glare can also be caused by reflected glare, which should not be confused with veiling reflections, which cause a reduction in visual performance rather than discomfort. VCP is based in terms of the percentage of people who will be expected to find the given lighting system acceptable when they are seated in the most undesirable location. Factors and Remedies Quality of illumination pertains to the distribution of luminaires in the visual environment. The term is used in a positive sense and implies that all luminaires contribute favorably to visual performance. However, glare, diffusion, reflection, uniformity, color, luminance, and luminance ratio all have a significant effect on visibility and the ability to see easily, accurately, and quickly. Industrial installations of poor quality are easily recognized as uncomfortable and possibly hazardous. Some of the factors are discussed in more detail below. Direct Glare. When glare is caused by the source of lighting within the field of view, whether daylight or electric, it is defined as direct glare. To reduce direct glare, the following suggestions may be useful: a. Decrease the brightness of light sources or lighting equipment, or both. b. Reduce the area of high luminance causing the glare condition. c. Increase the angle between the glare source and the line of vision. d. Increase the luminance of the area surrounding the glare source and against which it is seen. To reduce direct glare, luminaires should be mounted as far above the normal line of sight as possible and should be designed to limit both the luminance and the quality of light emitted in the 45–85 degree zone because such light may interfere with vision. This precaution includes the use of supplementary lighting equipment. There is such a wide divergence of tasks and environmental conditions that it may not be possible to recommend a degree of quality satisfactory to all needs. In production areas, luminaires within the normal field of view should be shielded to at least 25 degrees from the horizontal, preferably to 45 degrees. Reflected Glare. Reflected glare is caused by the reflection of high-luminance light sources from shiny surfaces. In the manufacturing area, this may be a particularly serious problem where critical seeing is involved with highly polished sheet metal, vernier scales, and machined metal surfaces. There are several ways to minimize or eliminate reflected glare: a. Use a light source of low luminance, consistent with the type of work in process and the surroundings. b. If the luminance of the light source cannot be reduced to a desirable level, it may be possible to orient the work so that reflections are not directed in the normal line of vision. c. Increasing the level of illumination by increasing the number of sources will reduce the effect of reflected glare by reducing the proportion of illumination provided on the task by sources located in positions causing reflections