canon RF 800mmf5.6 is canon 400mm f2.8 plus 2x teleconverter plus RF mount
rf 1200is just 600f4 plus teleconverter and RF mount.
Dunno why someone would pay a premium price for any of them when he can get 400mmf2.8 plus the teleconverter plus mount adapter for a cheaper price and have a more versatile equipment.
It's not the first time Canon does this, in the past they made FD 1200mmf5.6 then converted the same lenses to EF mount they even included teleconverters for some
https://en.wikipedia.org/wiki/Canon_EF_1200mm_lens
rf 1200is just 600f4 plus teleconverter and RF mount.
Dunno why someone would pay a premium price for any of them when he can get 400mmf2.8 plus the teleconverter plus mount adapter for a cheaper price and have a more versatile equipment.
It's not the first time Canon does this, in the past they made FD 1200mmf5.6 then converted the same lenses to EF mount they even included teleconverters for some
https://en.wikipedia.org/wiki/Canon_EF_1200mm_lens