An introduction to the science & practice of photography (1895)
Jones, Henry Chapman, 1854- · London, Iliffe, Sons & Sturmey Ltd · leaf 121
portraits, and portrait lenses have often been used for taking views. By common consent, lenses whose apertures are about one- sixth of their focal lengths are called universal, or portrait and group lenses ; if the aperture is one-eighth it is a view and group or simply a view lens ; if quicker… … Fig. 17. The first improvement on the telescope objective arranged as described above was by J. Petzval, the invention of whose portrait combination formed the first epoch in photographic optics. This lens was constructed by Voigtlander, of Vienna,
Photography
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