[davidmanze]

600/800mm f/11? Is it April 1st again? Not that I don't like the idea but I am probably in the minority about this.

I'm struggling to make any sense out of this telephoto strategy ....... 

 .......... who in the world would opt for a 600/800mm f11 .... is this the return to doughnut bokeh on a mirror-lens ???? 

......  not really adapted for sports, (light issues .. dim stadiums) ....
 ....... these are only useful for birding/nature where shutter speeds will be high and will lead to correspondingly high image noise even on the FF sensor  ..... so only " usable"  in bright sunny conditions.

The 150-600mm third party zooms have brought wildlife sports to the masses with affordable modest aperture lenses of F6.3 at the long end and have proved themselves ....... having the ability to zoom out for those larger creatures you have a half decent F5 for example ........ very practical !!

I can't think of any person saying to themselves.....

"I need an F11 600mm ...... because with it's 2X converter I have a 1200mm F22 lens.!!"...... errr yeah ?????

Actually I ran some tests on the Nikkor 600mm F4E ..... sharpness drops off at F11 from diffraction (slightly)..... 

  There are many nonsensical aspects to these two lenses and I can't see why anyone would choose them over any other lens manufacturer's sensible general purpose offerings! ....... are these a retractable design ??