The Dictionary Of Photography

A True Historic Record Of The Art & Practice Of Photography 100 Years Ago.

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distorting single lens, which works at a large aperture, which is free from distortion, without astigmatism, and has a very flat field (fig. 93). During the last few years great advances have been made, and new forms of lenses have been introduced, in the majority of which the optical glass manufactured at Jena is
Fig- 93-
employed. Messrs. Swift & Sons' lenses include fig. 94, a uni-versal paragon lens working at U.S. No. 2 orand fig. 95, Swift's portrait paragon, a symmetrical lens, working at U.S. No. I, or E. Suter of Basle has a series of aplanatic lenses, which work at U.S. No. 2, and also a very fine lens of the symmetrical
Fig- 94-
type, manufactured of the new glass, which works at No. 2 U.S., or With these the flatness of field is much increased, the angle of sharpness being about 6oo. He has also introduced a new wide-angle aplanat, which has an effective aperture offor an
angle of 60o andup to 900, this being illustrated by
fig 96. The field of this lens is very flat, and the front lens