In a sometimes more immediate way than prose, photographs can document and explain the sights and feelings of an era. In an exhibition opening Saturday at the Library of Congress, photographer Lewis Hine chronicles the working and social conditions of child laborers shortly after the turn of the century.
''Lewis Hine: Reformer With a Camera,'' comprises 61 images, copies of photographs taken from the original work by Mr. Hine which was presented to the library in 1954 by the National Child Labor Committee. The committee hired him in 1908 as a full-time investigative reporter.
Hine is acknowledged to want his photographs to be active, not passive, and to play a role in influencing people, particularly to take action against the abuses of child labor. He often manipulated his subjects to create startling effects and emphasize woeful inadequacies. The 5,000 photographs he took on child labor proved important in legislative efforts at setting a national minimum age of 16 for child workers.
Early in his career Hine photographed the new immigrants arriving at Ellis Island. Later, after his work in taking pictures of child laborers, he went to Europe for the Red Cross in 1918 to investigate and photograph the effects of World War I. In the 1920s he concentrated his efforts on man and the machine, culminating in the publication of the book ''Men at Work.'' In 1930, Hine photographed construction workers for the Empire State Building, and later documented Tennessee Valley Authority and Works Project Administration construction work.
The exhibition, which will close here Oct. 30, will tour extensively for the next two or three years.