Have you ever worn colored sunglasses? Some people prefer yellow or amber ones known as "blue-blocking" sunglasses. Others wear green, blue, or even red sunglasses to create a "look" or make a fashion statement. Unfortunately, everything viewed through those sunglasses appears to be yellow, green, blue or red! The same thing occurs under different color temperatures of artificial light, whether you use fluorescent or incandescent lamps.
Cool white fluorescent lamps emit yellow/green light. That is why objects viewed under the yellow/green light of fluorescent lights appear to have a yellow/green cast to them.
Warm white fluorescent light emits a reddish-orange light. I've heard it said that warm white light makes people look like the "Oompa-Loompa" characters in the Willy Wonka movies.
Only natural outdoor sunlight gives off the perfect color-balance of visible light for true color rendering.
In order for a light source to be considered "full spectrum" or "color-balanced" it must meet or exceed the following three criteria:
1. The Color Temperature of the light source must be greater than 5000K
2. The Color Rendering Index (CRI) value for the light source must be > 90
3. The Chromaticity Values (x and y coordinates) must reside in the central white portion of the Black Body Locus (below.)
The Color Temperature of sunlight changes dramatically during the course of the day. At sunrise and sunset, the color temperature of the sun is at 2000K. An hour later, the color temperature climbs up to 3500K. By noon, in Washington D.C., on a clear day, the color temperature has risen to 5400K. The question you must ask yourself is when it comes to matching colors, do you want to use the color of light you get at sunrise, or at noon?
Color Rendering Index refers to how accurately a color is perceived at a given color temperature of light. Try and think of the CRI value as a percentage. Sunlight, by definition, has a CRI value of 100, because it is perfect. If an artificial light source, say an incandescent light bulb, has a color temperature of 2500K, but a CRI of 100, then that means that any colored object viewed in that orange/red light source will be viewed as accurately as it can... in an orange-red light source!
Now, if you view an object under a 4100K light source (which tends to appear yellow/green) and the CRI is only at 61, then you can see that it would be very difficult to accurately match colors. This is why it is important to understand that if you want to accurately match colors, or if you just want the most natural, color-balanced light available, you must choose a light source that has a color temperature that is at least 5000K (sunlight at around noon), with a CRI of at least 90.
Chromaticity (or Lighted Appearance) as seen in the graphic (below) involves both an x and a y value. The closer the intersection of the x & y values are to the center of the white portion of the locus, the more accurate color rendering will be.
Any consumer who has shopped in a department store for clothing, or has shopped for carpeting, drapes, furniture, or paint understands the importance of color matching. They know that it is impossible to accurately match two colors under fluorescent lighting. One must bring the colored objects outside, under sunlight, to attempt the matching. Accurate color matching requires an accurate color rendering light source. For instance, electricians and electronic technicians know the importance of matching the different multi-colored bands present on wires. Beauticians know the importance of having the proper hair color or nail color to please their patrons. Doctors need to know the color of their patient's skin in order to determine whether their patient's flesh appears normal, cyanotic, flushed, jaundiced, or pallored.
Graphic artists, photographers, designers, and a myriad of other occupations demand excellent color rendering in order to perform their duties. Color-balanced light, by definition, is the presence of all seven (7) colors of the visible light spectrum (Red, Orange, Yellow, Green, Blue, Indigo and Violet) at or near the same spectral energy distribution proportions found in sunlight. Any light source that deviates from those proportions found in sunlight would not be considered color-balanced.
Today, there are "full spectrum" light bulbs available in the marketplace. They cost between $7.00-$35.00 per bulb. This is compared to the average cool white bulb, which only costs about $1.00-$2.00 per bulb at almost any hardware store. The only difference between these two lamp types is the types and colors of the phosphors coating the inside of the lamp. It is generally known that "full spectrum" lamps only remain full spectrum for about 5,000 hours, or one year. Even though they may still give off light, they are no longer full spectrum. If expensive full spectrum lamps are used, this becomes extremely cost-prohibitive!
Another consideration is that full spectrum light bulbs do not address the problem of UV transmission from the bulb itself. Most "full spectrum" lamps actually emit more UV than standard cool white lamps.
NaturaLux Filters provide color-balanced, scotopically enhanced light. Once fluorescent light rays pass through our filters, the result is a full visible spectrum of light, similar to that of natural outdoor sunlight. That means that any color viewed under a NaturaLux Filter should appear to be the same color, indoors and out.
As you can see, when it comes to accurate color rendering and improved visual performance, NaturaLux™ Filters are very good for business!
*Data supplied by Philips Lighting Company, Inc.
**Data supplied by Lighting Sciences Inc.
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