Elmar 50mm f/3.5

In 1925 Ernst Leitz II took a risk and launched the Leica I, the world's first practical 35mm camera designed around motion-picture film. The lens attached to every one of those first cameras was a 50mm f/3.5 designed by Dr. Max Berek — a modified Tessar formula with four elements in three groups that could be collapsed into the body for pocket carry. Without this lens there is no Leica story.

For beginners: f/3.5 sounds slow by modern standards but in 1925 it was entirely workable. The Tessar-type formula was chosen because it is compact, sharp in the centre, and relatively easy to manufacture to consistent tolerances. Berek's genius was adapting it to fit inside a body small enough to slip into a jacket pocket — previously "serious" cameras were the size of shoeboxes. The Elmar 50mm f/3.5 remained in production, in gradually evolved forms, until 1961: 36 years, a remarkable run that speaks to how right Berek got the original design.