522 



NEGRETTI AND ZAMBRA, HOLBOBN VIADUCT, B.C., 



Special quotations for larger sizes. 



166 



SERIES No. VI. 

 WIDE ANGLE APLANATS FOR COPYING, 



With a rapidity which is equal to Series V., these lenses give perfect flatness 

 of picture and sharpness of definition, and have, at the same time, a considerable 

 field. These qualities render them suitable for copying Maps, Charts, Pictures, 

 Engravings, &c., &c., &c. For inverting work for the printing process, we have 

 designed the prisms contained in Series VII. 



Special quotatitns for larger sizes. 



As a result of our experience, we beg to point out particularly the necessity of 

 avoiding the slightest vibration during exposure with these wide angle Aplanats. 



The passing of a cart, the working of a press on a contiguous floor, the 

 marching of soldiers in step, have been quite sufficient to affect that sharpness of 

 picture which is otherwise attainable with these objectives. 



In taking fine even objects, it is advisable not to use too small a diaphragm, as 

 the diffraction caused thereby veils the picture. 



3167 



SERIES No. VII. 

 PRISMS. 



These prisms are all right angle, with silvered hypothenuse ; they are centred 

 in their mountings, and adjustable to the lens by means of a screw in place of the 

 front ring of latter. 



To obtain parellelism between the anterior side of the prism and the object, 

 they are provided with an arrangement to turn the prism round its axis and to 

 clamp it in any position. 



