Review of Handbook of Applied Photometry

Abstract

Anyone who has attempted to make accurate photometric measurements will be uncomfortably aware that they are liable to more errors, and greater inaccuracy, than most other physical measurements such as mass, length, time or electric current. However, improvements are being made in a number of directions, which include the definitions of photometric quantities, and improved techniques and detectors. This handbook describes the state of the art; it has been written by ten experts working in industry or in government or international standards laboratories. As it is published in the USA, it is not surprising that most authors are also in the USA, but one is at the Bureau International des Poids et Mesures, France, and another at the Commission International de l'Eclairage (CIE) Central Bureau, Austria. Astronomical photometry has deliberately been excluded; polarization of light is mentioned, briefly, but only in the first chapter. Apart from these fields, I think the handbook is comprehensive. It will be useful mainly to those working in illumination engineering, such as highway engineers and architects, and also to astronomers concerned with light pollution of the sky. The first part of the handbook includes four chapters on the basics: these include clear definitions of light and radiation, and of terms such as luminance and illuminance, radiance and irradiance, and descriptions of photometric standards and detectors. Anyone now or recently working in photometry might safely skip these chapters. The second part of the book covers measurement procedures, case studies, photometric reports, and methods of spectroradiometry. Recent developments, such as automatic data-logging into a computer, promise to speed measurements and reduce costs. The last three chapters cover retroreflective materials and their measurement, colorimetry, and future trends. Every chapter ends with a list of references, from nine (Photometric and Radiometric Quantities) up to 157 (Colorimetry). The majority of these are very recent publications. In order to prolong the useful life of this book, the editor plans to establish a `Web Companion: a newsgroup for ongoing discussion about the book and related issues in photometry'. The URL for this, given in the preface, does not agree with that on the page facing the title page, and the e-mail address, which is the same on each page, does not work at present because of a server change. However, http://w3.osa.org/homes/Photonic/Groups brings up the OSA home page, from which it is possible to reach some more information about the authors. Until the list server is restored, comments and errata can be sent to the editor at casimer@vnet.ibm.com . The editor believes this is the first technical handbook to incorporate Web access. It is very difficult to avoid all misprints in a book of this length, and therefore unjust to judge it by these alone, but the description of the operation of a photomultiplier on page 117 is noteworthy: `The first element, the photocathode, is negatively biased and will eject photons when light is incident upon it...' And the explanation of the equation just below 1/2mv2 = hf - <DIV ALIGN="RIGHT">(4.6)</DIV> which is found on the next page includes ` is the incident flux (number of incident photons per second)'. In most other places it is the flux, but here it is the work function. An equation on page 157 has the left hand side, which is to be evaluated, as part of the denominator of the right hand side, which makes its evaluation a circular argument. In appendix A, Measurement Conversion Tables, miles are abbreviated to mi in the English to metric conversion table, but to m in the metric to English table, which will cause confusion with metres (or meters). In Area Conversion, 1 square meter = 1550 square centimeters (which should be inches). At the end of this appendix, `the same amount of light reaches the film if the camera is set for f/1.4 at 1/500 s exposure, f/1.4 at 1/250 s exposure, or f/2.8 at 1/125 s exposure'. Clearly the second setting should have been f/2.0 at 1/250 s. The proposed list of errata on the World Wide Web will be a valuable addition, and with it this handbook could become a reliable resource.