Gina Danatto, age 11, of Freeport, Ill., for her question:

WHEN WAS THE CAMERA INVENTED?

The camera was probably invented during the early 1500s. Historians give credit for the invention to many people including the great Italian artist Leonardo da Vinci.

The first crude camera was called the camera obscura or dark chamber. It was a darkened box with a tiny hole in one wall that admitted light. The light formed an image on the opposite wall. This image was an upside down picture of the scene outside.

The first camera obscura was actually large enough for a man to enter. By the early 1600s, the device was a sedan chair or a tent that artists carried into the countryside to sketch landscapes. They traced the lines and shapes of the image that came through the box, and then colored the picture.

During the 1660s, the camera obscura became a box about two feet long. A lens placed over the hole made the image larger and sharper. A mirror inside the camera reflected the image onto a piece of ground glass at the top of the camera.

In 1727, a German physicist named Johann Schulze discovered that silver salts are sensitive to light. He proved that light darkens silver salts. Schulze used sunlight to make images on silver salts but his images were not permanent.

The first person to make a permanent image was a French physicist named Joseph Niepce. He exposed a light sensitive metal plate in a camera obscura and then used an engraving process to "fix" the image. Niepce is credited with the "first photographs made by a camera."

In 1830, a French inventor named Louis Daguerre produced the first popular form of photography, the daguerreotype. He based his process on Niepce's work but developed the image with mercury vapor and "fixed" the image with common salt. Daguerre's process was perfected in 1839, and this date is generally accepted as the beginning of photography.

Also, in 1839, a British scientist named William Talbot invented a light sensitive paper.

Talbot's invention was the first negative positive system of making photographs. His friend, an astronomer named Sir John Herschel, named Talbot's invention "photography." Herschel also suggested the use of sodium thiosulfate (hypo) as a fixing agent. Both Talbot and Daguerre then began using hypo in their processes.

IN 1841, Talbot pattened the "calotype," an improved version of his process. He later called it the "talbotype." Talbot's process was not widely used because the daguerreotype produced a much clearer picture.

During the second half of the 1800s, scientists made great technical advances in photographic processes. With improved, easier techniques, more and more persons began to take pictures.

In 1840 a Hungarian scientist named Joseph Petzval designed a portrait lens and a landscape lens. The portrait lens transmitted 16 times as much light as previous lenses did. Petzval's landscape lens produced sharper pictures of large areas than had been possible before.