C. A. Steinheil Sohne, Miinchen. 



107 



symmetrical type led to the construction of smaller lenses of the 

 same class. 



Some of the universal aplanatic lenses consist of two cemented 

 doublets, others of two cemented triplets, but in all cases the combi- 

 nation is symmetrical. 



With the system of 6 lenses the principal points coincide with 

 the geometrical center of the objective, i. e. with the plane of the dia- 

 phragm. Distortion is thus obviated. 



This latter feature renders these objectives particularly adapted 

 for topographic photogTammetry and for copying. On account of their 

 rapidity the universal aplanatic lenses are specially intended for photo- 

 graphy of moving objects, which demand short exposures. 



The next four series of lenses are of the aplanatic type and have 

 been developed from the aplanatic prototype which originated in this 

 establishment (Bavarian patent of 1867). During these latter years these 

 lenses have been improved by the introduction of glasses which absorb 

 the chemical rays in a considerably less degfee than did the older 

 glasses. This improvement enabled the lenses to keep pace with modern 

 requirements. 



Series III : Aplanatic lens 1:7; 

 angle 60. Adaptable for por- 

 traits, groups, architecture, land- 

 scape, copying and sufficiently 

 rapid for instantaneous work. 



When it is required to delineate 

 plastic objects in correct proportions, 

 particularly in cases where the object 

 is not many times larger than the 

 image, these aplanatic lenses are also 

 specially supplied with very long focal 

 lengths. 

 Fig. 3. 



Series IV. Landscape Apla- 

 natic Lenses 1:12 to 1:15; 



field of about 75. Specially 

 constructed for landscape photo- 

 tography, but also adapted for 

 architecture and copying. 



Fig. 4. 



