Nikon F Reflex-Nikkor 1000mm f/11 mirror lens

introduction

this super telephoto lens was 1st introduced in 1965 and 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
NB. the 1st Nikkor mirror lens was designed for rangefinder cameras in 1959 and was a 100cm (1000mm) f/6.3 which had close focus of 30m and weighed 10kg!
the 1st version of a 1000mm f/11 was in 1965, had 5 elements in 5 groups and close focus to 8m
a new design was introduced in 1974 allowing for screw on rear filters instead of a turret design
the last version was introduced in 1976 and included NIC coating and improved handling
Nikon stopped making mirror lenses in 2005