see also:

• super telephoto mirror lenses
• a catalogue of Micro Four Thirds lenses

• this super telephoto lens introduced in 2011?? is a catadioptric mirror lens, and as with all such mirror lenses, share the following characteristics:
  • manual focus
  • fixed aperture (in this case f/6.3)
  • 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

• 300mm focal length and field of view (4° on Micro Four Thirds 2x crop) at infinity focus
• fixed f/6.3 aperture
• 13 lens elements, 11 groups (multicoated)
• closest focus 0.88m (1:2 macro)
• 55mm filter thread
• mm diameter, 66mm long and 298g
• cropped sensor camera mounts only - eg. Micro Four Thirds system (not full frame)
• ~$199

• ePhotozine review
  • focus can be difficult as three quarters of a turn takes you from infinity to 0.8m - it really needs a micro-focus gearing to enable accurate manual focus for distances > 10m
  • “good” sharpness in the studio but real world will likely be worse as poor focus accuracy is likely
  • 1.12EV vignetting; low contrast
  • minimal CA, minimal but complex pincushion distortion (~1%)
• http://www.thephoblographer.com/2012/09/10/first-impressions-tokina-reflex-300mm-f6-3-mirror-lens-micro-four-thirds/#.U3hC6ijm440