Instructions for midterm post

For the midterm:
The second half of the 19th century saw many, many important inventions and improvements to photographic technology. New processes were invented, new equipment, and new formats seized the public enthusiasm.

For this post you will select one such process, format or type of equipment and research its history. Your post will summarize for the others what happened, who and what was involved, and why it was important. Use illustrations and links to other sites as appropriate.