An old woman in Canton (Guangdong).

The photographs brought out the diversity of personalities of ordinary Chinese at that time, and highlighted China's street scenes, habits, dress codes and popular activities. They serve as interesting historical material as well as fine photographs.

"As a professional photographer, he had to make money by photographing the rich and famous. But he also photographed ordinary people with equal dignity," Yao says.

Thomson was born in 1837, two years before the invention of the daguerreotype, the first photographic process. After an early career working as an apprentice to an optician and scientific instrument maker, Thomson embarked on a journey in the 1860s to photograph countries in South and Southeast Asia.

In 1868 he arrived in Hong Kong and established a studio in Queen's Road in Central District. During this period, he photographed many of Hong Kong's mountain ranges, plains, rooftops and street scenes. During 1870-72, he made many journeys to Guangdong, Hainan, Fujian, Nanjing, Beijing, Tianjin, Taiwan and Macao.

On these travels, Thomson received much hospitality but also some hostility, as many Chinese people were not familiar with cameras and had never seen a Caucasian man.

But the challenges did not reduce Thomson's passion for photography. He stayed in China until 1872, and returned to Britain with three crates of glass negatives.