... and camera motion wants to be adjusted to either 3d or 2d ... to tell the story with the impact ... i am not sure, that just placing a third eye on the rig will do a good service ... either one of them will probably suffer ...
I would tell a 3d story completely different than a 2d story.
i would also think, that dramatic lighting may significantly change with each technique ...
guess, at the end it is like shooting two movies on one set, which in a double shot scenario may be tiring for the actors as well ... and then, the directors dilemma, getting a cool performance in one setup and missing it in the respective other ...
... alternatively, doing it both in parallel restrains the movement (and composition,as you have mentioned) of either one ...
sounds like a nightmare - creative process wise ...
given the "user experience" is what counts at the end ... (rather then the fame for having it pulled of)
Then:
Whatever the reasons of JC are, to shoot 60fps, he is right. ...

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