Metabones speedbooster: is there any reason to get full frame now?

Sorry, lost the thread there - you called it "cheating nature."

No one is claiming "perfection."  A design that is matched to a particular lens will preserve almost all of it's characteristics.  For this more general implementation that needs to work with many lenses, center contrast seems to be retained but some corner contrast will be lost.

Where did you get the idea that this is what I think? (Did I ever use the words "perfect" or "perfection"?)

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Erik