The first thing ever to resemble a photograph was created somewhere between 1839 and 1844 when William Henry Fox Talbot left a piece of lace on paper in the sun, creating a photogenic drawing and the first negative-positive photographic process.

“In the Darkroom: Photographic Processes Before the Digital Age,— a new exhibit at the National Gallery of Art, shows just how far photography has come since those first days.

The exhibition includes more than 100 photos dating as far back as 1839. It explores the changes in photography from the days when an object in the sun on a salt-soaked piece of paper produced an image to the innovations in color photography of the late 20th century, but it stops just short of the digital age that began in the 1990s.

The exhibit and the accompanying guidebook “provide a valuable overview of the medium as well as an introduction to the most commonly used photographic processes from its earliest days,— said Earl Powell, director of the National Gallery of Art.

The exhibit begins with the somewhat fuzzy photogenic drawing of lace created by Talbot. Talbot, who later became a noted photographer, soaked a piece of paper in a salt solution, allowed it to dry and then coated it with silver nitrate. Talbot then placed a piece of lace on the paper and left it in the sun. The paper darkened and created a negative of the lace.

The exhibit devotes several photographs to the daguerreotype in 1839, the first photographic process ever introduced to the public. The images were created by exposing a silver-coated copper plate to iodine and bromine. Each of these images is unique and can only be duplicated by being re-photographed.

“The daguerreotype really claimed the world’s imagination,— curator Sarah Kennel said.

This type of photography is shown in several prints, including one that was taken by Albert Sands Southworth and Josiah Johnson Hawes. The photo shows two women; one is holding a letter, but both are gazing off into the distance. The image is significantly sharper and more focused than the Talbot images.

A turning point for photography came in 1851 with the invention of the collodion negative on glass and the albumen print process. This allowed for photographs to have more differentiated tones. A good example is the photo “Fruit and Flowers— by Roger Fenton. The image is so clear that Kennel described it as “hyperclarified,— “lush— and “sensuous.—

“You feel as though you want to touch the fruit,— she said.

Later in the 19th century, the gelatin silver print came into existence, which paved the way for the film negative. This method continued to dominate the black-and-white photographs of the 20th century. These photos are familiar to most people and much more like the modern photos we see today.

The final part of the exhibit explores color photography in the 20th century. Although color photography was available in the 1930s, it wasn’t widely used until the 1970s. Such noteworthy artists as William Eggleston and Andy Warhol are featured in this section.

“In the Darkroom— takes great care to show visitors the difference between two photos of the same age that were taken using different methods. For example, the exhibit includes two prints of the 1855 photo “Portrait of a Woman and Child— by Jean Baptiste Frenet. Both images are created using salted paper and a collodion negative, but one is coated in wax. The photo without the wax is very faded, whereas the one with the wax is more golden and much clearer.

A book titled “In the Darkroom,— which delves further into the history of photography, accompanies the exhibit, which will run through March 14, 2010.