Calcium
Selenium
The metallic form of selenium conducts electricity over a thousand times more efficiently when light falls on its surface. For this reason its main use is in light meters, photocopier toner, photoelectric and solar cells.
One of the light meters pictured here is a Leningrad 8, made in 1985, presumably in Leningrad. Some of their light meters have the price printed on them from the factory, a sure sign of the Soviet command economy. One I came across was 75 roubles. Leningrad is also where the popular LOMO camera comes from, and it gets its name from this - Leningrad Union of Optics & Mechanics (the Leningradskoye Optiko-Mekhanicheskoye Ob'edinyeniye. The camera was originally intended as an espionage tool for KGB field agents.
