Gezicht op de ruïne van het Casa di Salustio te Pompeï

Sommer began his career as a professional photographer in Switzerland, where he documented the opening of a new roadway before 1857. By 1857, Sommer was located in Naples, where he established a studio. That same year, he travelled to Austria and Switzerland. In 1860 Sommer formed a partnership with German photographer Edmondo Behlès (1841-1921) in Naples. This partnership lasted until 1872. In 1861 Sommer photographed the camps and fortifications at Gaeta, Italy, Pompeii in 1863, and Capri, Messina and Rome, Italy in 1865. In 1880, Sommer photographed Palermo, Sicily, also producing views of monuments. Although based in Naples, Sommer sold views of all regions of Italy, often using negatives purchased from other photographers.