The present book is based on the experience of the author. The experience is mainly the result of years of research, of consulting work, and in participation in policy decision making in many felds, most, but not all, related to outdoor lighting. To some degree, the book represents the preference of the author. The selection of the subjects is based on more than 50 years of experience of what is desirable to know for persons engaged in scientifc research or practical application in the felds of lighting and vision. The subjects deal with a number of fundamental aspects. The theorists must have them at their fngertips, whereas the practical engineers may assume them as known in their daily work. The selection of subjects is based in part by the questions that came to the author over the years, but even more by the preference of the author himself. In this respect, it is a personal book. Thus, it should be stressed that the book is not a ‘handbook’ or even a ‘textbook’; many subjects that commonly are treated in such books are not included here. Not because they lack importance, but because the author feels that they are adequately treated elsewhere. Some relevant works are mentioned in the References. Over the years, the author has been engaged in giving courses on vision and lighting, lately more in particular on Masterclasses on a post-graduate or post-doctorate level.