a) Size and weight of the EF800mm 5.6 is a no go these days.It's curious that Canon didn't retro fit the EF 800mm f5.6 because it was a sharper and far superior lens optically than the EF400mm f2.8 with a dubious custom 2x teleconverter and integrated RF adapter version that was launched. However, it's AF and diaphragm limit the fps to 8 fps on the newer cameras. It's IS is of an old and legacy design too.
It points to issues around the amount of re-engineering requied to convert the IS, aperture and AF systems of the legacy lens, availability (they might not have held a lot of these in stock and didn't want to manufacture more) and the fact that Canon could easily re-engineer the bottom end of their large over supply of EF 400mm f2.8 mk III's and make 3 RF lenses with minimal outlay and high profit margins.
I think Canon wanted a "fast to market, low cost" solution and felt that this approach would be sharp enough. it also means that any future zoom variant only has this cobbled 400mm + TC to match resolution wise. It will never be measured against the EF predecessor.
It's barmy to think that a EF 400mm f2.8 LIS II with a 2x TC will outperform the current RF 800mm f5.6 in nearly every resolution metric. In fact this combo is only eclipsed by the native legacy EF 800mm f5.6 LIS.
b) the RF 800mm is excellent for closeup work. Using 800mm to shoot the elephant at the horizon generates blurry pictures no matter the glass....
Upvote
0