Despite being immersed in a time of innovation, William A. Pumphrey — like many photographers in the mid-1800s — used the then-emerging art form to express his distrust of the Industrial Revolution.

In one photograph taken by Pumphrey in 1855, two figures rest near a sewage-filled river. A cathedral rises above the town, depicting the contrast between the success of Britain’s past and the uncertainty of its future.

The photograph is one of about 120 featured in “Impressed by Light: British Photographs from Paper Negatives, 1840-1860,” which opened Sunday at the gallery. Many of the photographs in the exhibit focus on the past, rather than the innovation surrounding the photographers. The pictures show the grandeur of Madrid, the culture of British-ruled India and even farm life in rural Britain.

“People were not taking photos of the industrial world,” said Sarah Greenough, senior curator of photographs for the National Gallery of Art. “They found it very threatening because the old order was rapidly changing, so instead of depicting it, they turned their cameras to older, more traditional subjects,” she said. “All of them were very much looking backward trying to find a source and strength not in the new industrial world, but in earlier, more certain times.”

The photographs are among the first to be taken using a calotype, the precursor to the camera.

Although Louis-Jacques-Mandé Daguerre — a painter and physicist — created the daguerreotype around the same time that William Henry Fox Talbot invented the calotype, it was Talbot’s invention that paved the way for modern photography before the digital age.

Greenough said the exhibit is important because it has revolutionized the telling of photography’s origins. Until now, she said, most experts thought the calotype flourished upon its introduction but lost its popularity when a new method of photography that used glass instead of paper was introduced in 1851.

But the reverse was actually true, Greenough said. Upon its introduction, the calotype was mainly limited to small circles, she said. It didn’t emerge as a popular tool until about 1850, when people started seeing the calotype photographs in exhibits. Soon after, the calotype gathered momentum, especially among travelers who benefited from its light weight.

The first photographers who used the calotype were educated, but common, people who took up photography as an intellectual hobby, Greenough said. At the time, photography not only tested artistic knowledge but also some scientific knowledge.

Before taking a picture, the photographer had to “sensitize” ordinary writing paper. The the paper was dipped in saltwater, and when it was dry, a solution of silver nitrate and water was applied with a brush. The two mixtures chemically combined to make a light-sensitive silver chloride.

When the paper was placed in the calotype and exposed to light via mirrors that reflected the desired picture, areas on the paper that were hit with bright light turned a dark brown. This created a negative image, which was preserved and later placed on top of another sheet of sensitized paper. Both were then exposed to light. This allowed for more light to pass through the lightened areas of the negative to create an image on the paper beneath it.

Greenough said she found the photographers’ exploration into the art of photography, such as how to translate the world of color into one in black and white, particularly interesting.

“Many people would say art is all about breaking the rules and finding your own way to express your feelings and ideas about the world,” Greenough said. “What you see here are people really discovering the wonderful and magical ways that a camera could capture a moment and instant in time that’s important to them.”

“Impressed by Light” will be on display at the National Gallery until May 4. The museum is located at 4th Street and Constitution Avenue Northwest and is open Monday through Saturday from 10 a.m. to 5 p.m. and Sunday from 11 a.m. to 6 p.m.