# Colorimetry

UNITED STATES DEPARTMENT OF COMMERCE Alexander B. Trowbridge, Secretary NATIONAL BUREAU OF STANDARDS • A. V. Astin, Director
Colorimetry
I. Nimeroff
Institute for Basic Standards National Bureau of Standards Washington, D.C. 20234
National Bureau of Standards Monograph 104 (Supersedes NBS Circular 478)
Issued January 1968
For sale by the Superintendent of Documents, U.S. Government Printing Office Washington, D.C. 20402 • Price 35 cents
Library of Congress Catalog Card Number: 67—62079
THE NATIONAL BUREAU OF STANDARDS
The National Bureau of Standards provides measurement and technical information services essential to the efficiency and effectiveness of the work of the Nation's scientists and engineers. The Bureau serves also as a focal point in the Federal Government for assuring maximum application of the physical and engineering sciences to the advancement of technology in industry and commerce. To accomplish this mission, the Bureau is organized into three institutes covering broad program areas of research and services:
THE INSTITUTE FOR BASIC STANDARDS . . . provides the central basis within the United States for a complete and consistent system of physical measurements, coordinates that system with the measurement systems of other nations, and furnishes essential services leading to accurate and uniform physical measurements throughout the Nation's scientific community, industry, and commerce. This Institute comprises a series of divisions, each serving a classical subject matter area:
    — Applied Mathematics — Electricity — Metrology — Mechanics — Heat — Atomic Physics — Physical Chemistry — Radiation Physics — Laboratory Astrophysics- — Radio Standards Laboratory, which includes Radio Standards Physics and Radio Standards Engineering — Office of Standard Reference Data.
THE INSTITUTE FOR MATERIALS RESEARCH' . . . conducts materials research and provides associated materials services including mainly reference materials and data on the properties of materials. Beyond its direct interest to the Nation's scientists and engineers, this Institute yields services which are essential to the advancement of technology in industry and commerce. This Institute is organized primarily by technical fields:
    — Analytical Chemistry — Metallurgy — Reactor Radiations — Polymers — Inorganic Materials — Cryogenics- — Office of Standard Reference Materials.
THE INSTITUTE FOR APPLIED TECHNOLOGY . . . provides technical services to promote the use of available technology and to facilitate technological innovation in industry and government. The principal elements of this Institute are:
    — Building Research — Electronic Instrumentation — Technical Analysis — Center for Computer Sciences and Technology — Textile and Apparel Technology Center — Office of Weights and Measures — Office of Engineering Standards Services — Office of Invention and Innovation — Office of Vehicle Systems Research — Clearinghouse for Federal Scientific and Technical Information — Materials Evaluation Laboratory—NBS/GSA Testing Laboratory.
* ↑ Headquarters and Laboratories at Gaithersburg, Maryland, unless otherwise noted; mailing address Washington, D. C, 20234.
* ↑ Located at Boulder, Colorado, 80302.
* ↑ Located at 5285 Port Royal Road, Springfield, Virginia 22151
Foreword
NBS Circular 478, Colorimetry, was issued 1 March 1950 and has been reprinted several times in response to a continuing demand. Such have been the advances in colorimetry that in 1965, instead of authorizing another reprinting of a work obsolete in many details, I asked Mr. I. Nimeroff to up-date it. I am grateful to him for undertaking this tedious but important task, and I am much pleased with the result.
Deane B. Judd
Assistant Division Chief,
Metrology Division
Colorimetry
I. Nimeroff National Bureau of Standards Washington, D.C. 20234
The definition of color, as a characteristic of light, and the basic principles of its measurement are given. The reduction of spectrophotometric data to three chromaticity coordinates by means of the three-function CIE standard observer system for colorimetry is described. Various methods of direct colorimetry, and visual and photoelectric methods of colorimetry by differences from material standards are treated. The most useful collections of material color standards are described and the most widely used one-dimensional color scales are explained. The limitations of several colorimetric methods: spectrophotometric, photoelectric, and visual, are discussed.
| Key Words: | Color dictionaries, color vision, colorimeters, photoelectric tristimulus, spectrophotometric colorimetry, visual colorimetry. |