Reflex mirror and other improvements (contd.)
In 1685, Johann Zahn, a monk from Wurzburg, solved the
final piece in the optical puzzle. Improving upon Sturm's
design, he introduced lenses of longer and shorter focal
lengths. Scenes as wide as a landscape or as close as a
portrait could be viewed with a simple change of lens.
Page from “Oculus”, Johann Zahn,