PREFACE This new edition of the International Lighting Vocabulary - Chapter 845 of the International Electrotechnical Vocabulary - is the result of intensive work carried out by the Technical Committees of the International Commission on Illumination (CIE) and of the International Electrotechnical Commission (IEC) to supplement and update the contents of the previous edition (1970). In addition@ new subjects have been introduced@ in particular quantities relating to photons to complement those relating to energy and photometry@ a section on the actinic effects of optical radiation as well as several terms relating to luminaires for mine illumination. Despite these additions@ the volume of this vocabulary has been kept within acceptable limits by eliminating less important terms and the terms of general physics1) which appeared in the previous edition. It is not the purpose of this vocabulary to go into greater detail and provide explanations of use to the experts in each specialized field; this is the province of the appropriate Technical Committee. The preface of the 1970 edition gave the historical background of this vocabulary@ the first edition of which was published in 1938. In 1975 it was decided to prepare the present edition when the relevant Committees were entrusted with the initial revision work on the subjects in their domain. The proposals of most of these committees considered at a first joint CIE-IEC meeting held in 1978 enabled the main lines for the presentation of this edition to be decided. Four years of discussion were necessary to harmonize the elements presented by the Technical Committees and it was not until September 1982 that the draft vocabulary was ready for submission to the National Committees of the CIE and the IEC2) when it met with the unanimous approval of the voters. Finally@ a joint CIE-IEC Editing Committee made some editorial changes based on the comments accompanying the votes of the National Committees. The English and French versions were thus completed at the beginning of 1984@ and were subsequently supplemented by the translations into German and Russian and by the terms only of the other five additional languages of the IEC's International Electrotechnical Vocabulary (IEV). The alphabetical indexes in the nine languages complete the volume. The aim of this edition of the International Lighting Vocabulary comprising some 950 terms and their definitions is to promote international standardization in the use of quantities@ units3)@ symbols3) and terminology in this field. 1) These terms are given in Chapters 111 : Physics and Chemistry@ and 121 : Electromagnetism@ of the IEV which are grouped together in the Handbook: Vocabulary of Fundamental Concepts. 2) Documents l(1EV 845)(C0)1171 amended by 1(IEV@ 845)(C0)1199 (under the Two Months' Procedure) and l(1EV 845)(C0)1191 circulated under the Six Months' Rule and their respective Reports on Voting l(1EV 845)(C0)1198@ l(1EV 845)(C0)1213 and (IEV 845)(C0)1214. 3) In accordance with IEC Publication 27-1: Letter Symbols to be used in Electrical Technology Part 1: General; with IS0 Standard 31/0: General principles concerning quantities@ units and symbols@ and ISO-3 1/6: Quantities and units of light and related electromagnetic radiations. Non-standardized symbols used in these chapters are designated by brackets. EX. 845-01-33[G]