Derogy Paris Petzval

Petzval lenses are in big demand these days.  Joseph Petzval’s design of 1839 responded to the need for wider apertures for shorter exposure times, offering an open aperture up to f/3.6, good centre sharpness and a very smooth fall-off.  A feature highly-prized by modern photographers is the swirly effect in out-of-focus backgrounds, although it only really happens round the edges if you use a lens on a format larger than it was designed for.

Paris became the centre of Petzval manufacture in the latter half of the 1800s, with dozens of makers churning them out.  Derogy was the first to “mass produce” Petzval lenses, starting around 1850.  This lens has no serial number, and no slot for Waterhouse stops (aperture plates) which dates it to before 1858, a very early example.  Focal length is 320mm at a fixed aperture of f/4.5.  To use the lens in daylight, with film, Pete designed the slip-on shutter (see below).  This allows speeds from 1/20s – 1/250s and makes shooting outdoors perfectly viable.  The lens doesn’t quite cover 10×8″ at infinity, so the corners vignette quite markedly, but for pure vintage appeal it’s hard to beat.