The Periskop is an early symmetrical camera objective developed by Steinheil. The Periskop is used with a central f-stop
<div style="display:inline-block;padding:0 3px;background-color:#CCF">Original:</div> <div style="display:inline-block;padding:3px 0;"><a href="//commons.wikimedia.org/wiki/User:Trinitrix" title="User:Trinitrix">Trinitrix</a></div> <div style="display:inline-block;padding:0 3px;background-color:#CCF">Vector: </div> <div style="display:inline-block;"><a href="//commons.wikimedia.org/wiki/User:Loki_66" title="User:Loki 66">Loki 66</a></div>
2011-06-17
Own work based on: <a href="//commons.wikimedia.org/wiki/File:Periskop_Objective_graph.jpg" title="File:Periskop Objective graph.jpg">Periskop Objective graph.jpg</a> <i>by</i> <a href="//commons.wikimedia.org/wiki/User:Trinitrix" title="User:Trinitrix">Trinitrix</a>