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A set of pictures by the German photographer Albert Frisch have sold at auction in Sotheby's in New York.

The pictures were taken more than 150 years ago during an expedition to Brazil's Upper Amazon and are believed to be the earliest photographic record of the area. Frisch's pictures capture both the natural landscape and its indigenous inhabitants of among others the Ticuna, Miranha and Caixana tribes.

The collection comprises 98 albumen prints which were first published in 1869 by publisher Georg Leuzinger.

Frisch took up photography in 1863 and moved to Rio de Janeiro the following year where he started working for Leuzinger. It was he who commissioned Frisch to produce photographs of the undisturbed Amazon.

Frisch set off in November 1867 covering nearly 1,000 miles on foot or by boat over the next five months. He produced more than 120 glass plate negatives using the wet collodion process which required him to travel with a portable laboratory.

The process meant that the photographic plates had to be prepared moments before they were exposed in the camera with development taking place immediately while they were still wet.

Many of the pictures are in fact layered or composite negatives with Frisch often photographing his sitters and backgrounds separately giving the pictures a sculptural feel.

Frisch's photographic career only lasted a few years but his prints are still held in a number of collections around the world.

All photographs courtesy Albert Frisch / Sothebys