Vivitar Series 1 800mm f/11 Solid Cat mirror lens

introduction

this super telephoto lens introduced in mid-1970's 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
designed by OPCON Associates, a company founded by Ellis Betensky, who used to be a senior optical designer at Perkin-Elmer
their ruggedness is partially due to their solid, one-piece construction, unlike most production mirror lenses

800mm focal length and field of view (3.1°) at infinity focus
fixed f/11 aperture
lens elements, ? groups, VMC coating
closest focus 7m
lens cap ?112mm
rear filter
- needs to always be used with a rear filter attached, because the optical design relies on the presence of one more glass element with specific thickness
T lens mount thread
may not be able to mount on some cameras if the built-in flash of the camera protrudes too far
metal hood is only 1“ long
108mm diameter, 84mm long and 1.36kg