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. Light was 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.