Children work on farmland. Gao liang

Crook writes in the autography: "Against this background of backwardness and poverty and toil and oppression, the peasants maintained an impressive dignity and self-respect, a sense of humor, an eloquence full of vivid imagery and an ingenuity with which I could not compete."

It's a love for China and its people that made the couple stay for 40 years.

"Their photos show a desire to communicate and have woven the thread of photographic history in China," says Gao Chu, the exhibition's co-curator and a researcher on Chinese photographic history.

He says no more than 2,000 photographic plates and limited text about land reform have been preserved.

"The Crooks' photos captured the economic structure and social order of a typical village of North China, which would complement our research on reform," he says.