Thanks to a number of documents of the time, it is now certain that "Negretti and Zambra"'s photographs of China and Japan were taken by Rossier, but for many years it was thought that they might have been taken by either Walter B. Woodbury, who also had dealings with "Negretti and Zambra" but was based in Batavia (now Jakarta), or Abel Gower, who was an amateur photographer in Japan. The Leiden University photograph collection includes a portrait, allegedly of Gower, signed "P. Rossier", and in 1859 Rossier and Gower shared passage aboard "HMS Sampson" from Nagasaki to Edo.