Invention

Part 10 - Photography

1110 PHOTOGRAPHY (510) 21031179 200127 (1789)https://www.youtube.com/watch?v=JoxGEymA8ro Good short

The earliest known description of the camera obscura is found in Chinese records from the 4th century BCE. Until the 16th century, this was a tent with a pinhole that projected an upside down image, from outside, onto a dark surface inside the tent. (The name Camera Oscura comes from Latin meaning a dark chamber or room). 

It was used mainly to study optics and especially to safely watch solar eclipses without damaging the eyes. Around 1550, the simple pinhole was replaced with a biconvex lens in a wooden box and a mechanism to reduce the aperture was added in 1568 thereby reducing the amount of light entering the camera. These improvements gave brighter and sharper images but did not provide a permanent record.

In 1558 Giambattista della Porta recommended the camera obscura as a drawing aid, the image could be traced over to create an accurate picture and thus the box type camera obscura became the basis for the first photographic cameras.

In the 13th century, Albertus Magnus noted that silver nitrate would blacken skin and, in 1614, Angelo Sala noted that powdered silver nitrate exposed to sunlight turned black as ink.

Around 1717, Johann Heinrich Schulze exposed a bottle of a slurry, containing some silver particles dissolved in a mixture of chalk and nitric acid, to direct sunlight. He discovered that letters stencilled on the bottle created an image of the letters on the slurry.

In 1777, the chemist Carl Wilhelm Scheele discovered that silver chloride was darkened when light formed microscopic dark particles of metallic silver. He also found that ammonia dissolved the silver chloride, but not the dark particles, a process that might have been used to "fix" a camera image captured with silver chloride.

Scheele also noted that red light did not significantly effect silver chloride, an effect that would later be applied in photographic darkrooms as a way to view black-and-white prints without affecting their development.

Inspired by Scheele's writings, Thomas Wedgwood may have been the first person to think of using a camera to create a permanent image on a surface coated with a light-sensitive chemical. About 1790 he discovered that images of a camera obscura, were too faint to affect a silver nitrate solution. He corresponded with James Watt and Humphry Davy about his experiments with 'Silver Pictures' but neither were able to solve the problem of fixing the image.

In France, in the late 1830s, Joseph Nicéphore Niépce exposed a pewter plate, coated with bitumen, to an image on a portable camera obscura and discovered that the image did not fade quickly. Niépce collaborated with Louis Daguerre to create the daguerreotype in January 1839. This was a copper plate was coated with silver and exposed to iodine vapour before it was exposed to light. The daguerreotype required up to 10 minutes of exposure but it produced clear, finely detailed images that were very popular until the invention of emulsion plates in the late 1850's.