Photography is based on the fact that certain silver salts undergo a physical transformation upon exposure to light, causing them to darken. The first person to capture a photographic image was Joseph Nicéphore Niépce. 
He accomplished in 1814 this using a camera obscura, a large darkened room into which a person would enter, and could view an inverted image of light that passed through a lens or small opening on one side of the room and was projected onto the opposite wall. His image required 8 hours of exposure and eventually faded. Niépce then began experimenting with Louis-Jacques-Mandé Daguerre to find a way to make the captured image permanent. After Niépce’s death, in 1837, Daguerre developed the daguerreotype, a more practical method of photography. He found a way to fix the image on paper and it only required 30 minutes of exposure.
The first photographic process to use the system of negatives and positives commonly used today was discovered by William Henry Fox Talbot in 1841. Using this technique, an unlimited number of positive images could be created from a single negative. This process, called the calotype, used paper negatives treated with a silver nitrate solution. Once exposed to light and fixed, the negatives were waxed to make them translucent so that the positive images could be printed. 
In 1851, Frederick Scott Archer made advancements to photography in his invention of the collodion process, which only required 2 to 3 seconds of exposure. This process used a glass negative that had to be exposed while wet.
George Eastman invented a flexible, dry film. He used this film, which could be rolled up and introduced the Kodak camera in 1888. The camera was filled with enough film for 100 exposures. Once these pictures had been taken, the whole camera could be sent back to Kodak, where the images were developed and printed and the camera was reloaded with new film. This made photography available to everyone, even those who were unfamiliar with the development process. In 1913, Oscar Bernack invented the first 35 mm camera, much like the ones we use today. Photography has developed from black and white pictures that were blurry and required long exposure times to full color images that require only a fraction of a second to capture, and using certain lenses, more detail can be seen than can be seen by the human eye. Perhaps if photography was in Degas’ time what it is today, he would have found it more useful to his paintings.