The Photic Field brings a formal elegance and completeness to the portion of geometrical optics that deals with amounts of radiant energy. Since the time of Lambert, this discipline has been handled piecemeal by a great variety of methods. But by utilizing the full potentialities of field theory, the book unifies the subject and forges a powerful tool for handling practical applications. Such applications include solar heating, lighting design, photographic exposure, and color specification. The pharosage vector is used throughout the book, and divergence, curl, and gradient are employed. Potentials and quasi-potentials are important, and contour integration allows a double integral to be replaced by a single integral. These and other aspects of field theory will allow the reader to solve photometric problems that were previously difficult to formulate. Many of the formulations in geometrical optics, although conceptually clear, are computationally unwieldy. As a result, researchers until quite recently have had to rely on a scattered collection of rules of thumb and approximation methods. But now, with the general availability of computer, exact solutions are within range, and thus many of the equations given in The Photic Field may be directly applied almost for the first time.