P.J.C. Janssen(1824-1907)

Pierre Jules César Janssen was a French astronomer born in Paris into a cultivated family. He studied mathematics and physics at the faculty of sciences, then taught at the Lycée Charlemagne in 1853, and in the school of architecture from 1865-1871, but his energies were mainly devoted to various scientific missions entrusted to him. In 1868, he discovered the gaseous nature of the solar chromosphere and, along with English scientist Joseph Norman Lockyer, the element helium. In 1874, in order to capture a series of photographs of transit of Venus, Janssen invented the Revolver of Janssen or Photographic Revolver, an instrument that originated the chronophotography (a branch of photography based on capturing movement from a sequence of images). This was a large camera based on the Maltese cross mechanism, which is an important milestone in the development of cameras used to film movies. The revolver could take several dozens of exposures at regulated intervals on a daguerreotype disc. Later this invention was of great use for researchers like Étienne-Jules Marey to carry out exhibitions and inventions. Janssen's series of photographs covering the transit of planet Venus captured in Passage de Venus (1874) was a pioneering and historic register that survived the test of time and is considered by many as the oldest film ever created, possibly the very first where moving images were used.