The 3-D-3 Rangefinder and Depth of Field Indicator

Abstract

A wander mark stereoscopic rangefinder using the normal eye separation as Its base length is described. It has two main controls: one carries a scale of ranges and could be coupled to the focusing mechanism of a camera lens; the other carries a scale af lens apertures and could be coupled to the stop setting mechanism of the lens. Three indicating marks appear In space at variable distances from the observer, to show the range and depth of field limits set by the controls. The optical system consists of an illuminated diapositlve, a collimating lens and three partially reflecting mirrors. It gives autamatic campensation for varying eye separations of different observers, is accurate and easy to use, even by spectacle wearers. The rangefinder affers advantages aver established methods of setting focus In both still and cine photography, particularly in low light and on moving subjects. Under these conditions the depth of field indication is a valuable asset.