The recording of this meeting is available below!

Since ancient times, chemists, physicists, mathematicians, and others were involved in discovering various methods of capturing and saving images. PHSNE’s October program is dedicated to the 185th anniversary of photography. It will focus on innovators whose discoveries caused revolutionary changes in the field. The discussion will be led by PHSNE member Vladimir Khazan.

The discovery of the camera obscura that provides an image of a scene dates back to ancient China. Chinese philosopher Mozi (470 to 390 BCE) stated that the camera obscura is a “collecting plate” or a “locked treasure room”. Camera obscura (Latin for “dark chamber” is a light tight room or box with a pinhole allowing light to go through, creating an image on the opposite wall. The camera obscura produced temporary images that were used by artists as a painting aid, but it could not capture or save an image.

The discussion will touch on German Professor Johann Heinrich Schulze’s 1724 discovery about silver nitrate which darkens when mixed with chalk due to exposure to light rather than heat, the thinking at the time. He used the phenomenon to temporarily capture shadows. His work launched a chemical era in photography.

Khazan will talk about Thomas Wedgwood who used chemicals and the camera obscura to obtain an image, though he was unable to save the image. He will touch on the first surviving photograph taken and saved in 1826 by Joseph Nicéphore Niépce and go on to the discovery by Sir John Herschel that silver nitrate reacts with halides to give images different colors and Herschel’s observations, shared with other researchers in 1839, that hyposulphite makes pictures permanent.

In 1841, William Henry Fox Talbot patented a process for paper negatives which he called calotypes. It made it possible to print multiple copies from one original. Talbot brought exposure time down to seconds. In 1844 he compiled a book illustrated with photographs, all images taken by him. The book demonstrated the limitless possibilities of photography in various fields: architecture, portraying, copying, etc.

Photo sources in order of appearance:

• https://blackcreek.ca/how-to-make-your-own-camera-obscura/
• https://commons.wikimedia.org/wiki/File:Johann_Heinrich_Schulze_(HeidICON_33573).jpg
• https://en.wikipedia.org/wiki/View_from_the_Window_at_Le_Gras