Toronto. Even before 1839, optical houses created various lenses from glass for the apparatus of the day. After 1839, lens design and quality became the defining factor of camera quality.
Most optical institutes such as Zeiss provided lenses to a multitude of makers. Some institutes however, offered only a few lens designs of reputedly superior quality. For example, Leitz created for its Leica what they claimed were high quality lenses. When the bayonet model Leicas were introduced after the second war, lenses were named for their widest aperture. A summicron was f/2 for example, and came in various focal lengths. In later years Leitz added -M for lenses designed for their bayonet cameras and Apo- for lenses that brought three primary colours into a flat image plane.
Regardless of the maker, lenses always used a number of elements of various curves and glass or transparent crystal types. Today, Caltech in the States is experimenting with image creation by an optical phased array (OPA). Science Daily in their Science News column for June 22, 2017, headlines that, “Ultra-thin camera creates images without lenses – New design substitutes an array of light receivers for a lens, making cameras thin, light, cheap, and flexible”. This technology potentially makes zoom lenses or multiple prime lenses unnecessary as well as allowing ultra thin cameras!
If you have a scientific curiosity browse the Science Daily site. My sincere thanks to member, speaker and table holder emeritus Russ Forfar for bringing this article to my attention. Perhaps one day our cameras will be almost as thin as a book page is today!