Voigtlaender & Sohn. Braunschweig. 143 



tectural photography became the most popular branches of amateur 

 photography. For these purposes, however, the portrait lens, with its 

 different degrees of rapidity was not very suitable, owing to its limited 

 field. Frederick von Voigtlaender, the fourth and present head of the 

 firm, subsequently constructed in 1877 the Euryscopes, symmetrical 

 lenses which gave a large flat and bright field quite free from distortion. 

 These lenses having rapidly become popular, various successive 



F F 



series were constructed of relative apertures ^r, -^r and Wide Angle 



lenses of relative aperture -^. These correspond to the series IV, VI, VII 

 and VIII of the present catalogue. The advantages of the symmetrical 

 lenses suggested also improvements in portrait lenses, and in 1883 the 

 long focus portrait lenses were replaced by symmetrical Portrait Eury- 

 scopes. (Series II and III of the catalogue). 



Until comparatively recently opticians had only a limited range of 

 optical material at their disposal. The series of available glasses was 

 uniformly graduated according to the percentage of lead contained in the 

 glasses. The optical properties of these glasses varied monotonously: 

 a higher percentage of admixed lead always resulting in higher refractive 

 and dispersive powers. 



Great changes were effected in this direction when Prof. Abbe 

 and Dr. Schott established the Jena Glass Works and in 1886 published 

 their new glasses. The production of these new glasses influenced the 

 optical industry in a similar manner, though to a much greater extent, 

 as did Fraunhofer's 7 glass-fusions. In the new series practical opticians 

 found at last glasses, whose optical properties appeared to be paradoxical; 

 there were glasses of high refraction and low dispersion and there were 

 others of high dispersive and low refractive power; within certain limit 

 it was even possible to couple any desired dispersion with any given 

 refractive index. 



Messrs. Voigtlaender & Sohn have been the first opticians who 

 utilized this extension of the optical means in as much as they comple- 

 tely reformulated in 1888 their symmetrical lenses, which until then had 

 contained two flint-glasses, and replaced the latter by two extremely 

 transparent crown-glasses. The Rapid Wide Angle Euryscope Series V, 

 the W. A. Euryscope Series VII and the Single Landscape Lenses IX 

 were introduced as new species of photographic lenses. 



Although all these new constructions embodied great improvements 

 in definition and covering power, yet it was not possible with the symme- 

 trical objective TO compensate thoroughly astigmatic aberrations, the chief 

 defect of wide angle lenses. By employing a totally dissymmetrical com- 

 bination of pairs of glasses of normal and abnormal properties the firm of 

 CarlZeiss of Jena has recently succeeded in almost completely eliminating 

 this last defect. Since the spring of 1891 Messrs. Voigtlaender & Sohn 

 have by friendly arrangement with the firm of Carl Zeiss, added to their 

 older series these Zeiss Anastigmatic lenses, of which 6 series classified 



F F i 



according to their relative apertures from - 4 to jg are now made. 



