see also:

• super telephoto mirror lenses

• this super telephoto lens introduced in 1974 is a catadioptric mirror lens, and as with all such mirror lenses, share the following characteristics:
  • manual focus
  • fixed aperture (in this case f/11)
  • virtual elimination of chromatic aberration as uses mirror rather than lenses
    • also means focus position for infrared photography is the same as for light photography
  • central mirror:
    • allows much more compact lens length as the optic path is reflected internally twice
    • by necessity, blocks some of the light and thus causes:
      • decrease in image contrast
      • characteristic “doughnut” shaped bokeh imagery in out of focus areas

• 1600mm focal length and field of view (1.6°) at infinity focus
• fixed f/11 aperture
• lens elements, ? groups (multicoated)
• closest focus
• mm filter thread but mount turns when you focus + mm rear filter
• mm diameter, mm long and g

• Minolta Flashback