Based on some properties of the visual caustic test, the author has developed a photographic technique capable of rendering an objective document about the features of concave optical surfaces which are measurable with the visual caustic test. The plates are measured in a machine capable of measuring in two coordinates and are reduced following well known methods. The agreement between the visual and photographic methods is good and improves at high D/F ratios. Drawings of the apparatus are presented along with measurement and reduction sheets and graphs comparing the visual method and photographic technique. The complete paper will be published elsewhere.Asociación Argentina de Astronomía