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Color 101: Color Rendering

Understanding the principals of light and color temperature is only the tip of the iceberg when trying to control lighting.

Taking into consideration the principals of how color is produced and interpreted by the eyes, there is a third piece to the puzzle of controlling lighting. This third aspect is an indirect interaction between the light source and the eyes called Color Rendering. Color rendering is a method or measure of how a light source makes objects appear. This might be somewhat confusing. Take into consideration light temperature and the variations in light color based on wavelength. Since not all light is the same or uniform, the appearance of objects will vary dependent upon the color of light shined on them. This effect is measured by the Color Rendering Index. Like color temperature, the index amounts to just another accurate way of gauging the effects of certain light sources. The Color Rendering Index is a measurement from 0 to 100. Similar to color temperature, this measures the wavelength of light emitted by a particular light source or bulb. However, unlike color temperature, this index is an indirect measurement. Color temperature is used to measure the specific range of visible light by a bulb. Color rendering is a measurement of how light appears when reflected off physical objects. When light strikes an object, the color of the particular object is the only wavelength of light that is reflected, all other colors are absorbed by the object. When a person looks at the particular object it appears a particular color, because its the only color reflected by the object. This being a description of perfect circumstances is the reason color rendering must be understood. A particular bulb will emit light within certain range of wavelengths. Depending upon the range of light the bulb creates, its effects on perception of the physical world will vary. For example, light that is skewed toward the cooler or more yellow end of the spectrum, will emit a yellowish light. When this yellow tinted light strikes objects is will produce a dull and mellow light because it only contains a small portion of the visual spectrum. The inverse is true of bulbs that emits brighter blue-white light. These bulbs emit light across the full spectrum and will make any color appear to glow. For a homeowner its essential to understand how color rendering works in order to create the desired visual appeal of the interior or exterior of a home. When using the Color Rendering Index as a buying tool, consumers should be aware of the the differences in products. Bulbs in the 100 value range of the index emit full spectrum light. Logically the scale of the index, 0 to 100, is used to denote the percentage of the visual spectrum the a light gives off. The lower the number on the index, the more yellow or red the light will appear because it will only give off light at the lower end of the spectrum. Specific types of light bulbs behave differently. Incandescent lights will typically have a color rendering of 100. This due to the age and prevalence of the technology. Because manufacturers have sought to raise profit margins by limiting the variety of bulbs, the easiest solution was simply to produce a full spectrum light. Fluorescent lights are a much newer technology, and are constantly evolving, so their color rendering properties will vary. Older fluorescents sit just above 50 on the index, however modern compact fluorescents will emit light in the 95 range on the index. The bulb itself is only half the battle. Lamp shades and light fixtures themselves have a significant impact on light coloring. Since shades are often features designs or patterns of a particular color, the light shade itself will act as a color filter letting on certain light through. Making use of lamp shades that achieve the desired color rendering effect is not difficult, but does require a degree of conscientious attention from the homeowner. The best way to provide full spectrum light is to make use of blue or white shades and fixtures. Cooler light is achieved through shades and fixtures colored or tinted red, orange and yellow.