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What is Prime-Color, Inc.?

Prime-Color, Inc. (PCI) was a privately held and family-run N.J. corporation.  PCI was incorporated in 1983 by Dr. William A. (Bill) Thornton.  Bill Thornton was a leading color scientist with 50 years experience in lighting, color and vision.  He also holds 45 U.S. patents, has published some 80 articles and has lectured around the world.  

PCI’s mission centers on the modern understanding of how human vision works and how this affects the lighting professional.  We have two goals:

  •           Produce meters that measure light, color and brightness as the human visual system does.  These meters are unique in providing their user with a substitute for expert human evaluation.  See “Metering the Visual Characteristics” below.

  •          Communicate, to workers in color and the general public, exactly what to expect of human color vision.

PCI leads the industry both in understanding the “prime-color” approach to human color vision and developing products based on that knowledge.

What are the “Prime-Colors”?

Long ago people sensed three principle colors in the world of color and lighting.  These three colors have been discussed since 1700 by color scientists such as Palmer, Wunsch, Young, and Maxwell.  More recently, Wright, MacAdam, and others noted that one or more of these colors seemed to play distinctive roles of some sort.

Around 1965 our founder, Bill Thornton, discovered the reasons for and significance of this behavior.  Human color vision responds most strongly at three points in the visible spectrum, blue-violet near 450 nm, pure green near 530 nm, and orange-red near 610 nm.  He named the colors at these points the “prime-colors.”  These three colors appear more bright because humans “see” more strongly there, not because the spectrum was somehow stronger there.  The prime-colors rule how and what people see in ordinary life, as well as in commerce.  They mark the three peaks in the sensitivity of the normal human visual system.  In 1978 Westinghouse Corporation awarded Bill their highest honor, the 'Order of Merit', "for the development of the prime-color principle...the most important advance in fluorescent lighting in 20 years...and for his many contributions to the understanding of color phenomena."

Bill Thornton next put the prime-colors to use by inventing the "tri-phosphor lamp", or "triband lamp", or "prime color lamp."   These lamps produce “prime color white light”;  white light made up of the prime-color wavelengths.  Lamplights designed to produce “prime color white light” do not waste energy in wavelengths humans won’t respond to, an energy savings.  Such lamplights produce beautiful coloration in whatever was lighted by them, a customer benefit.  Light that includes the non-prime colors diminishes color rendition!  In 1979, Bill Thornton received the US National 'Inventor of the Year' by the Association for the Advancement of Invention and Innovation in a ceremony at the US Patent Office.  The basic patents on prime-color lamps were chosen above 60,000 US patents that year for this award!

Sears Roebuck made the new lamps their Corporate Standard, saving $10 million annually in electrical energy, plus a large part of $50 million in customer merchandise returns because of the clarity of store lighting.  Manufacturers Hanover saved $233,000 in one 22-story building the first year using prime-color flourescent lamps, replacing standard lamps one-for-two.

Metering the Visual Characteristics

We call "the many effects of lamplight on the appearance of an illuminated scene”, the characteristics of that lamplight.  These characteristics separate into two very different groups: the old fashioned or “physical” characteristics and those involving the human visual system or “visual” characteristics.

Old-fashioned physical characteristics like footcandles, color temperature, color, and color rendering index are easy to compute from a simple count of how much light falls throughout the spectrum.  They are based on long-standing rules and equations that do not consider the modern understanding of how humans see.  Our competitors’ meters measure just these characteristics--according to these rules and equations.

Visual characteristics like color-attractiveness, color-scheme-stability, perceived brightness and visibility are based on human vision.  They cannot be simply computed.  Historically, they have been best judged by consensus, using a group of human observers with normal color vision.  After all, "illumination" has little meaning except as it relates to human activities, as judged by human observers.  In the past the only way to get a reliable evaluation of illumination was to:

  •            Gather a group of expert and unbiased observers

  •            Have them study and judge a complex colored scene illuminated by the lamplight

  •           Compare these judgments to those of many other diverse lamplights

  •          Employ satisfactory scientific procedure and analysis

An alternative first appeared to the public in 1987 when Bill Thornton was granted the patent for the original PCI Illumination Quality (IQ) Meter.  This meter broke new ground by including and using the gathered mass of visual data: Years of research encapsulating thousands of hours of observation by dozens of expert observers viewing hundreds of lamplights were compressed in mathematical form and programmed into each IQ meter.

When an IQ Meter was asked to evaluate a lamplight it follows these steps:

·            A precisely calibrated spectroradiometer determines the power of the lamplight across the spectrum, called the “spectral power distribution” or SPD of that lamplight.

·            A computer evaluates the physics of the SPD and calculates the “physical” characteristics.

·            The computer searches among the IQ Meter’s mass of data on the visual characteristics of the many illuminants (lamplights) stored in its memory.

·            It interpolates among these to arrive at the proper values of the visual characteristics for the new lamplight.

The IQ Meter need never have seen the lamplight now being measured.  It can sense all the characteristics of a lamplight by merely 'looking' at the lamplight.  It doesn’t need a complex colored scene.  It puts numbers on the visual characteristics using several new scales that value the characteristics as would the "average person".  It also calculates all industry standard and old-fashioned measures so as not to force the user into unfamiliar territory.

Only IQ Meters can substitute for a group of talented experts—which you don’t always have at your elbow!  The “IQ” in our meters was because they’re smart...each one has the knowledge of many expert observers tucked inside!

Brightness & Footcandles …inaccurate? How does PCI help?

Unfortunately, the prime-color lamps which produced such dramatic successes in the early 1980s are no longer available.  They require a slower and more precise manufacture,  but  the materials and techniques are available.  The largest obstacle to their manufacture and acceptance lies within industry standards.

The widely accepted CIE Standard Observer teaches that any footcandle of light was as bright as any other, regardless of their colors.  But even back in 1955, Chapanis and Halsey showed that red and green lights are about twice as bright as yellow light, and blue light can be roughly ten times brighter.  And now “prime-color white” light was brighter still.  Prime color lamplight yields fifty percent greater perceived brightness than does standard fluorescent lamplight at equal watts, yet lumen outputs (footcandles) are 20-30% lower.  How do we explain this difference?  At their worst, the lumen and footcandle differ by over 100% from expert visual judgment of the brightness of a scene!

A similarly old fashioned measure of color rendering was the color rendering index (CRI).  The CRI measures how a lamplight renders colors compared to how real daylight renders colors, not how a human observer would assess color “trueness”, “pleasantness”, or “clarity”.

Of course we should only care about how humans perceive light and color!  But official agencies, including the CIE and the US government, retain the lumen and footcandle.  This forces manufacturers to compete in a marketplace of specifications touting lumens, footcandles and CRI, not in the real world of human-perceived brightness and color rendition.  As in other industries “specmanship” replaces reality.  Commercial lamps have been forced to revert to their higher lumen but lower brightness forms.  The energy saving features and color rendering capability of illuminants based on prime-colors go unrealized.

PCI uniquely understands the shortcomings of these old-fashioned criteria.  A first step toward resolving the problem was for workers in the color and lighting industries to gain hands-on access to both old and new characteristics as they work.  Our IQ Meters do exactly that, they supply both the modern visual measurements and the old-fashioned physical ones.

  •             Was the office lit brightly enough for painstaking paperwork?

  •             Does the restaurant illumination make food look appetizing?

  •             Does the concert hall enable a patron to read his program and yet highlight the orchestra on the stage?

  •             Does the lighting in the hospital room encourage the patient by benefiting his appearance, to his own satisfaction and that of his visitors?

  •             Does the lighting in the hospital room at the same time make diagnosis easy for the medical practitioner?

  •             Does the hotel lobby lighting yield attractive coloration of guests and decor?

  •             Will the draftsman in the proposed engineering complex be able to work long hours without visual fatigue?

With an IQ Meter in hand, the user is no longer at the mercy of lamp manufacturers, industry standards and the underlying “specmanship”.  The user can now know exactly what his customers will enjoy about the lighting, and what he must change.

Where can I get More Information?

PCI’s founder, Dr. William A. Thornton, has made many breakthroughs and contributions to the field of color science.  These form the basis for PCI’s unique offerings.  For more information please consult his many publications.
Postal address
26 Devonshire Way, Jackson, NJ 08527
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