In obtaining the optimum lighting design, we have been apt to depend considerably upon the experience including a vast amount of photometric data. It takes much time to determine the aiming points of floodlights and to repeat the illuminance calculation many times, and so on.
For these reasons, it has been desired to develop the lighting design theory which is simple and free from failure with no dependence on the experience.
The theory here introduced satisfies these needs. The method is, fundamentally, carried out in the reverse order of the point-by-point method. Assuming a lighting tower to be a large light source, the gonio-photometric intensity (luminous intensities in all directions) is calculated from the illuminances on a given lighted area. The type of floodlight and the aiming points are determined such that they approach to the predetermined intensities. Finally, the calculation of illuminance is to be done by the point-by-point method using the determined data (the distribution, the aiming points, and so on).
This method is available especially for the case of symmetric distribution type floodlights. As for the asymmetric distribution ones, some problems remain for further investigations.