106 



C. A. Steinheil Sohne. Miinchen. 



delineated images. The lenses become thus eminently suited for projection and 

 enlarging. 



The original and enlarged negatives may be produced by_ the same anti- 

 planetic lens. In the latter case it is, however, necessary to reverse the lens, 

 i. e. to place it so that the posterior lens faces the original which is to be enlarged. 



Enlargements of very sharply defined originals produced by this method 

 may be made to exhibit depths which are unobtainable by direct photography 

 with the same rapidity. 



The dissymmetrical antiplanetic lenses are made in two types: 



Series I. Portrait Antiplanet, 



Relative aperture 1:4, angle 40 T 

 four lenses with positive cemented 

 anterior pair and isolated negative 

 posterior pair. The field is limited 

 as a means of obtaining unusual 

 brightness. The latter and defi- 

 nition are uniformly distributed 

 over the image and the lens 

 possesses considerable depth. 



Series II. Group Antiplanet, 

 1:0, angle 60: four lenses, two 

 cemented pairs: these are placed 

 as closely together as the inter- 

 position of the diaphragm will 

 admit of. 



This lens is of only moderately 

 diminished brightness as compared 

 with the preceding series, but its 

 peculiarities have been utilized in in- 

 creasing both its depth and the field 

 without diminishing its uniformity of 

 definition and distribution of light. 

 Fig. 2. These united qualities render the group 



antiplanets adaptable to a great many uses, which .accounts for the popularity 



of this series. 



Universal Aplanatic Lenses. Relative aperture 1:6, angle 60. 



These lenses originated in the endeavour of constructing objectives of the 

 same rapidity as the group antiplanets but having larger dimensions. The latter 

 type did not appear to be adapted for this purpose on account of the rapid in- 

 crease of the thicknesses of the lenses necessitated by increase of focal length, 

 and, consequently, increase of weight and diminution of rapidity. 



The excellent results obtained with the new series of the rapid 



