293 H. TAVERNER ON A SIMPLE METHOD OF TAKING STEREO-PHOTO- 



scopically than by my former method. I therefore tried the 

 experiment of cutting out all the central rays of light by means 

 of a stop placed behind the objective, having a circular aperture 

 so situated that its inner edge was outside the optic axis of 

 the lens (Fig. 1, b). The resulting photographs were a decided 

 improvem ent on those obtained by my former method, and on 

 showing these to Mr. Rheinberg he confirmed me in my intention 

 of experimenting with stops of smaller aperture. I do not 

 think I need say anything further on this point, except to 

 mention that all the photographs on exhibition to night were 

 taken with stops having circular apertures of 2| to 4 mm. in 



Fig. 1. 



diameter, and with the inner edge of the aperture in no case 

 more than 1 mm. from the optic axis of the lens. It will 

 be found necessary to vary the size of the aperture in the 

 stop according to the thickness of the object to be photographed 

 and the objective in use ; but the best results, without distortion 

 or exaggerated stereoscopic relief, are to be obtained by the 

 use of a stop having : — ■ 



1. The largest possible aperture that will give sufficiently 

 sharp detail in the picture. 



2. The inner edge of the aperture as near the optic axis 

 of the lens as will give sufficient stereoscopic relief and, at the 

 same time, the truest appreciation of the thickness of the object, 

 or third dimension. 



