DIY Optical Viewfinder 35mm

This is an optical viewfinder to be used on a rangefinder camera such as Leicas, FEDs or Zorkies when using wide angle lenses such as Zeiss Biogon or the russian Jupiter-12 lenses. Unlike the built-in viewfinder of your FED or Leica,which is made for 50mm lenses, this viewfinder should give you the correct angle of view for 35 mm wide-angle lenses.
It may also be useful on a digital camera when you can't or dont want to use the screen.
The viewfinder will fit onto the standard hot- or colds