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CONTENTS
PREFACE ix
1 INTRODUCTION: MAKING LIGHT COUNT 1
1.1 Organization of chapters 4
1.2 Terms 9
Notes 10
2 LIGHT AS A LAW-ABIDING QUANTITY 12
2.1 Beginnings 12
2.2 A lawless frontier 18
2.2.1 Photography: juggling variables 20
2.2.2 Astronomy: isolated forays 21
2.3 Techniques of visual photometry 22
2.3.1 Qualitative methods 22
2.3.2 Comparative methods 22
2.3.3 Physical methods 24
2.4 Studies of radiant heat 24
2.5 Describing colour 26
Notes 28
3 SEEING THINGS 33
3.1 Recurring themes 34
3.2 Altered perceptions 36
3.2.1 Astrophysics and the scientific measurement of light 37
3.2.2 Spectroscopy 41
3.2.3 Shifting standards: gas and electrotechnical photometry 42
3.2.4 Utilitarian connections 43
3.3 The 19th-century photometer 49
3.4 Prejudice and temptation: the problems in judging intensity 53
3.5 Quantifying light: n-rays versus blackbody radiation 58
Notes 64
4 CAREERS IN THE SHADOWS 72
4.1 Amateurs and independent research 72
4.2 The illuminating engineers 75
4.3 Optical societies 86
A History of Light and Colour Measurement
Notes 88
5 LABORATORIES AND LEGISLATION 94
5.1 Utilitarian pressures 94
5.2 The Physikalisch-Technische Reichsanstalt 96
5.3 The National Physical Laboratory 99
5.4 The National Bureau of Standards 102
5.5 Colour at the national laboratories 104
5.6 Tracing careers 107
5.7 Weighing up the national laboratories 109
5.8 Industrial laboratories 111
5.9 Wartime photometry 114
5.10 Consolidation of practitioners 116
Notes 117
6 TECHNOLOGY IN TRANSITION 125
6.1 A fashion for physical photometry 125
6.1.1 Objectivity 126
6.1.2 Precision 128
6.1.3 Speed 129
6.1.4 Automation 129
6.2 The refinement of vision 130
6.3 Shifts of confidence 133
6.4 Physical photometry for astronomers 135
6.4.1 An awkward hybrid: photographic recording and visual
analysis 135
6.4.2 A halfway house: photographic recording and
photoelectric analysis 137
6.4.3 A ‘more troublesome’ method: direct
photoelectric photometry 139
6.5 The rise of photoelectric photometry 142
6.6 Recalcitrant problems 148
6.6.1 Talbot’s law 148
6.6.2 Linearity 148
6.6.3 The spectre of heterochromatic photometry 150
Notes 151
7 DISPUTING LIGHT AND COLOUR 159
7.1 The Commission Internationale de Photom´etrie 161
7.2 The Commission Internationale de l’ ´ Eclairage 162
7.3 Legislative connections 167
7.4 Constructing colorimetry 168
7.4.1 Colour at the CIE 168
7.4.2 Disciplinary divisions 176
7.4.3 Differentiating the issues 177
7.5 Voting on colour 179
vi
Contents
7.5.1 Configuring compromise 180
7.5.2 An uncertain closure 181
Notes 184
8 MARKETING PHOTOMETRY 191
8.1 Birth of an industry 192
8.2 Technological influences 194
8.3 Linking communities 197
8.3.1 Extension of commercial expertise 200
8.3.2 New practitioners 201
8.4 Making modernity 203
8.5 Backlash to commercialization 204
8.6 New instruments and new measurements 206
8.7 Photometry for the millions 208
8.8 A better image through advertising 210
Notes 213
9 MILITARIZING RADIOMETRY 220
9.1 The mystique of the invisible 220
9.2 Military connections 221
9.2.1 British research 222
9.2.2 American developments during the SecondWorld War 222
9.2.3 German experiences 224
9.2.4 Post-war perspectives 225
9.2.5 New research: beyond the n-ray 227
9.2.6 New technology 227
9.3 New centres 229
9.4 New communities 230
9.5 New units, new standards 231
9.6 Commercialization of confidential expertise 232
9.6.1 New public knowledge 232
9.7 A new balance: radiometry as the ‘senior’ specialism 233
Notes 233
10 AN ‘UNDISCIPLINED SCIENCE’ 237
10.1 Evolution of practice and technique 237
10.2 The social foundations of light 240
10.3 A peripheral science? 243
10.3.1 On being at the edge 243
10.3.2 Technique, technology or applied science? 245
10.3.3 Attributes of peripheral science 247
10.4 Epilogue: declining fortunes 248
Notes 250
BIBLIOGRAPHY 255
Abbreviations 255
Periodicals 255
vii
A History of Light and Colour Measurement
Organizations 257
Other 258
Sources 258
Notes 261
Bibliography 261
INDEX 272
PREFACE
This book is about how light was made to count. It explores a seemingly
simple question: How was the brightness of light—casually judged by everyone
but seldom considered a part of science before the 20th century—transformed
into a measurable and trustworthy quantity? Why did the description of colour
become meaningful to artists, dyers, industrialists and a handful of scientists?
Seeking answers requires the exploration of territory in the history, sociology and
philosophy of science. Lightwas made to count as a quantifiable entity at the same
time as it came to count for something in human terms. Measuring the intensity
of light was fraught with difficulties closely bound up with human physiology,
contentious technologies and scientific sub-cultures.
Explorations often begin with meanderings, tentative forays and more
prolonged expeditions. This one ranges over a period of 250 years, and pursues
social interactions at every scale. As the title hints, the subject was long on the
periphery of recognized science. The illustrations in the book reinforce the reality
of social marginalization, too: depictions of light-measurers are rare. Certainly
their shrouded and blackened apparatus made photography awkward; but the
reliance on human observers to make scientific measurements came to be an
embarrassment to practitioners. The practitioners remain shadowy, too, because
of the low status of their occupation, commercial reticence and—somewhat
later—military secrecy.
The measurement of brightness came to be invested with several purposes.
It gained sporadic attention through the 18th century. Adopted alternately by
astronomers and for the utilitarian needs of the gas lighting industry from the
second half of the 19th century, it was appropriated by the nascent electric lighting
industry to ‘prove’ the superiority of their technology. By the turn of the century
the illuminating engineering movement was becoming an organized, if eclectic,
community promoting research into the measurement of light intensity.
The early 20th century development of the subject was moulded by
organization and institutionalization. During its first two decades, new national
and industrial laboratories in Britain, America and Germany were crucial in
stabilizing practices and raising confidence in them. Through the inter-war period,
committees and international commissions sought to standardize light and colour
measurement and to promote research. Such government- and industry-supported
ix
A History of Light and Colour Measurement
delegations, rather than academic institutions, were primarily responsible for the
construction of the subject.
Along with this social organization came a new cognitive framework:
practitioners increasingly came to interpret the three topics of photometry (visible
light measurement), colorimetry (the measurement of colour) and radiometry (the
measurement of invisible radiations) as aspects of a broader study.
This recategorization brought shifts of authority: shifts of the dominant
social group determining the direction of the subject’s evolution, and a shift
of confidence away from the central element of detection, the eye. From the
1920s, the highly refined visual methods of observation were hurriedly replaced
by physical means of light measurement, a process initially a matter of scientific
fashion rather than demonstrated superiority. These non-human instruments
embodied the new locus of light and colour, and the data they produced stabilized
the definitions further.
The rise of automated, mechanized measurement of light and colour
introduced new communities to the subject. New photoelectric techniques
for measuring light intensity engendered new commercial instruments, a trend
that accelerated in the 1930s when photometry was taken up with mixed
success for a wide range of industrial problems. Seeds sown in those
years—namely commercialization and industrial application, the transition from
visual to physical methods and the search for fundamental limitations in light
measurement—gave the subject the form it was to retain over the next halfcentury.
Nevertheless, changing usage mutated the subject. Light proved to be
a valuable quantity for military purposes during and after the Second World
War. A wholly new body of specialists—military contractors—transformed its
measurement, creating new theory, new technology, new standards and new units
of measurement.
Following this variety of players through their unfamiliar environments
illuminates the often hidden territories of scientific change. And two themes
run throughout this account of the measurement of light and colour from its
first hesitant emergence to its gradual construction as a scientific subject. The
first traces changing attitudes concerning quantification. The mathematization of
light was a contentious process that hinged on finding an acceptable relationship
between the mutable response of the human eye and the more readily stabilized,
but less encompassing, techniques of physical measurement. The diffident
acceptance of new techniques by different technical communities illuminates their
value systems, interactions and socio-technical evolution.
A second theme is the exploration of light measurement as a science
peripheral to the concerns of many contemporary scientists and the historians
who later studied them, and yet arguably typical of the scientific enterprise.
The lack of attention attracted by this marginal subject belies its wide influence
throughout 20th century science and technology. Light measurement straddled
the developing categories of ‘academic science’ and mere ‘invention’, and was
influenced by such distinct elements as utilitarian requirements, technological
x
Preface
innovation, human perception and networks of bureaucratization. Unlike more
conventionally recognized ‘successful’ fields, the measurement of light did not
evolve into an academic discipline or technical profession, although it did attract
career specialists as guardians of a developing body of knowledge. By studying
the range of interactions that shaped this seemingly diffuse subject, this book
seeks to suggest the commonality of its evolutionary features with other subjects
underpinning modern science. This richly connected region, belatedly gaining
attention from historians and sociologists of science, has too long been in the
shadows.
Perhaps unsurprisingly, the initial motivation for this study came from my
own background as a physicist in industry and academe, and from doctoral work
in the history of science. My acknowledgements are equally diverse. Charles
Amick, Dick Fagan and William Hanley of the Illuminating Engineering Society
of North America, Susan Farkas of the Edison Electric Institute, David MacAdam
at the Institute of Optics in Rochester, Deborah Warner of the Smithsonian
Institution, and the librarians of the Universities of Leeds and Glasgow helped
in locating source material. Geoffrey Cantor, my doctoral supervisor during
the time much of this work was gestated in the History of Science Division
of the Philosophy Department at the University of Leeds, gave continual warm
encouragement and advice, and Graeme Gooday, Colin Hempstead, Jeff Hughes
and colleagues at the Universities of Leeds and Glasgow provided welcome
suggestions, discussions and/or interest in my subject and draft at various stages.
Some of the material in this book has appeared previously in the journals
Science in Context and History of Science, and benefited from the comments of
anonymous referees. Portions of this work presented at meetings also elicited
supportive discussion, particularly those organized by the British Society for
the History of Science (Edinburgh 1996), the CNRS Maison des Sciences de
l’Homme (Paris 1997), the Society for the History of Technology (London 1996
and Baltimore 1998), the University of Gothenberg (G¨oteborg 1998) and the
Katholieke Universiteit Leuven (Leuven 2000). Comments at those conferences
from Jaap van Brakel, Bruno Latour, Barbara Saunders, Terry Shinn and John
Staudenmaier were particularly helpful. I am no less grateful to Charles Thomas
Whitmell, whose name appeared with surprising regularity as the collector of
documents that attracted my attention at Leeds1.
I dedicate this work to my family: to my parents, who planted the seeds of
my interests; to my wife Libby, who nurtured them and supplied constant support
and encouragement; and to my sons Daniel and Samuel.
Sean Johnston
Dumfries, April 2001
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