From 1839 to 1860 circa, cameras had lens without stop. They could be big or small and the exposing materials weren't very reliable. A few lens of that period still survive. From 1860 to 1890 stops began to propagate (Waterhouse stops in 1858) and the lens improved a lot; there were field cameras and studio cameras, always in big frame sizes. The first shutter systems came (like Lancaster, Thornton-Pickard etc.) to control the influx of light. From 1890 to 1920 Anastigmat lens and shutters appeared after a period of "Rapid", "Symmetrical" and "Rectilinear" .