art - craft
Alfred Hrdlicka was an Austrian sculptor, painter, and professor. His surname is sometimes written Hrdlička.
Johann Zahn (German: Johann or Johannes Zahn) was a German scientist and philosopher, optician and astronomer, mathematician and inventor.
Zahn studied mathematics and physics at the University of Würzburg, was professor of mathematics at the University of Würzburg, and served as a canon of the Order of Regular Canon Premonstratensians. His other activities were optics as well as astronomical observations.
In 1686 Johann Zahn invented and designed a portable camera obscura with fixed lenses and an adjustable mirror, which is the prototype of the camera. In his treatise on optics, Oculus Artificialis Teledioptricus (1702), Zahn gives a complete picture of the state of optical science of his time. He begins with basic information about the eye and then moves on to optical instruments. The book is aimed at eighteenth-century microscope and telescope enthusiasts and includes all the necessary details of construction, from lens grinding to drawings.
