First published in the American Singers Club newsletter, July 1999.
The health benefits of sunshine has been a well known fact for many years; however publicity about the negative effects of over exposure to direct sunshine on the eyes and skin sometimes leads to erroneous conclusions.
A recent press release from London noted that "the bugs causing sick building syndrome" the phenomenon thought to prompt several ailments, including headaches, tiredness, and flu-like malaise "could be eradicated with ultraviolet lights." High intensity UV lights installed in an office block in Montreal were found within three weeks to almost wipe out the bacteria and fungi growing in ducts and ventilation equipment. A survey of 113 employs who never knew whether or not the lights were on, found that 20 percent fewer work-related symptoms occurred when the lights were on.
Following publication of my article on lamps that can be expected to promote canary songs. I received a letter from a gentleman that sells lighting supplies. A couple of his statements require close examination. For instance, "Vitalights are overpriced 3-4 times, the major lamp manufactures make equals at much less cost, i.e., Chroma 50 at $5.00." This statement shows a lack of full understanding of the characteristics of fluorescent lamps. The only thing "equal" about the two lamps are the color temperature rating. The color rendition index (CRI) of the two lamps are radically different, therefore in no sense of the word are they equal. The primary reason for the differences in cost is the addition of rare earth phosphors which increases the cost of the lamp. The second point I wish to make is the loose use of the term "Full Spectrum Lighting" by many manufacturers. Does this mean the lamp output closely matches the color output and other characteristics of sunshine? The answer to this question is definitely not!
From a catalog supplied by the aforementioned lighting supply salesman the following material appears "Generally, the higher the CRI, the better the colors appear."
|Type||Color Temp. (Kelvin)||CRI (color rendition index)|
|Cool White||4150 K||62|
|Lite White||4150 K||62|
|Warm White||3000 K||52|
|Deluxe Daylight||8500 K||84|
|Chroma 50||5000 K||90|
|Vitalight Supreme||5500 K||96|
|Noon sunlight||5250 K||100|
The color-rendering index (CRI), attempts to describe how the colors will appear when illuminated by a light source of specified chromaticity (color temperature). However, there are limitations to it's use which should be recognized. Although the system provides for ratings up to 100, it can only be used to compare sources of approximately the same chromaticity. As noted in the above chart Deluxe Daylight cannot be compared to the Chroma 50 due to the much higher color temperature of the Deluxe Daylight (8500 K). In general the higher K rating is whiter, the lower K rating is yellow. Except for the Vitalite bulb, none of the others emit ultraviolet. It should be recognized that direct exposure to sunlight results in several hundred times more ultraviolet exposure than that of the Vitalite bulbs, hence no health issues should be of concern. Birds do benefit from direct exposure to sunlight, however most of us do not have the luxury of outdoor facilities.
The widely used advertising for "Full Spectrum Lighting" does not mean the lamp is equivalent to sunshine as no ultraviolet is emitted. There is a special ultraviolet lamp marketed for germicidal purposes, but neither humans or animals should be exposed directly to the rays.
The only way to actually determine how closely a lamp matchs up to sunlight is to compare a color spectral distributions chart of sunlight to the color spectral distribution chart of an individual lamp. The International Commission on Illumination has specified the amount of light generated in each color by a light source being measured. This consists of six colors (purple, blue, green, yellow, orange and red). In addition, a spectral distribution chart measures the amount of mid ultraviolet and near ultraviolet. The standard is based on natural outdoor light at 5500 K and a color rendition index of 100.
Incandescent bulbs and standard Cool White or Warm White fluorescents render only partial spectrums so colors and objects viewed under these light sources are not seen accurately. In work situations, this can lead to eye strain, headaches, fatigue and eventually to a loss of productivity. In addition, it is believed that birds vision is significantly different from humans when ultraviolet is present. Tests have been conducted on school children to determine the degree of behavior problems experienced where different wall color schemes were used. It was determined there were significant differences in behavior depending on the wall color.
Copyright © 1999 Bill Summers. All rights reserved.
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