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Competitive Analysis, Color Rendering in White Light
Comparing Metal Halide, Fluorescent, and Solid State Technologies
by Jim Dilbeck, Cireon

Scope

This study compares the color rendition characteristics of the three most common commercial lighting
technologies; HID (high pressure sodium and metal halide), fluorescent, and solid state.

This document addresses the color rendition of the white light used in commercial ambient lighting and
the perception of color relative to the industry’s only color measurement scale.

This document is a cursory overview. The subject of color rendition is addressed conceptually here as it
relates to the present measurement techniques and human eye perception. The science is extensive
and addressed here in fundamentals only; much of this subject is beyond the scope of this document.

Objective

Providing a comparison between measured and perceived color, the consumer of commercial lighting
will better understand how their spaces will appear, specifically how colors will look under each of the
three commercial technologies considered herein.

We intend to show that significantly too much emphasis is put on the Color Rendering Index (CRI) score.
Few understand how the CRI works or how a light source with a CRI of 25 can be perceived as having
better color rendition than a CRI of 80. This fact is the primary objective of this paper.

Providing an understanding of how CRI is derived should simultaneously provide an understanding of
where the scale applies, where it is misleading and, more specifically, why it should not be used to
compare lighting sources across technologies.

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Overview

Every human eye has a varying degree of color sensitivity; some of us see color extremely well and
others not so. As we age, our ability to discern color decreases. As there is no “standard” human eye,
the truth is that color rendition is subjective.

The following details how color is rendered by the output of a light source being reflected off of an
object to the eye. Supporting this is unbiased data comparing the color emissions of the three most
common commercial ambient light sources; metal halide, fluorescent, and solid state.

There is a lot of controversy regarding how color should be measured and how the results should be
portrayed. This is because the present method, the Color Rendering Index, though suitable for the
comparison of HID and fluorescent, is inadequate in the measurement of solid state lighting.

We’ll also touch on the pending change to the more recently developed Color Quality Scale (CQS).

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