The most important work ever produced in the field of physiological optics, this classic is a model of scientific method and logical procedure, and it remains unmatched in its thorough and accessible approach. This is the second in a three-volume republication of the definitive English translation of Handbuch der Physiologischen Optik, originally published by The Optical Society of America in 1924 and containing everything that was known about physiological optics up until that time. The substratum consists of the data that Helmholtz furnished in the two nineteenth-century German editions that appeared during his lifetime. These volumes also contain extensive supplementary matter that Nagel, Gullstrand, and Kries incorporated in the third German edition of 1911, as well as significant new material prepared for the 1924 English translation by C. Ladd-Franklin, Gullstrand, and Kries, with copious annotations by James P. C. Southall that brought the work up to date with current research. The first volume in this series explores the dioptrics of the eye; Volume II examines the sensations of vision, including stimulation by light; simple and compound colors; intensity and duration of sensation of light; and variations of sensitivity and contrast. Appendixes cover later findings on adaptation, twilight vision, and the duplicity theory; normal and anomalous color systems and theories of vision; and the nature of color sensations. The succeeding volume considers perceptions of vision.

This book is a translation by Professor Sami El Hage of Volume I of Le Grand's three-volume treatise on physiological optics. It is the last of the three volumes to be translated into English. Le Grand's second volume was translated into English by Hunt, Walsh and Hunt and published in 1957 under the title Light, Colour and Vision. His third volume was translated into English by Millodot and Heath in 1966 and published under the title Form and Space Vision. Although Le Grand's three volumes have been compared to the three volumes of Helmholtz, it is important to note that Le Grand has distributed differently the topics in his three volumes. This book is a mixture of the tradition established by Helmholtz and followed by Tscherning and Sheard with the tradition originated by Danders and followed by Landolt and Laurance and others. Helmholtz's first volume was concerned with the image forming structure of the eye, almost without reference to practical problems of examining patients and fitting them with glasses. It dealt with the problems of a single eye.