[wim]

I reckon the 100-400mm doesn't offer sync IS because it's a Sigma lens - possibly featuring Sigma's miserable OS (not compatible to sync-IS ...) - which would explain the mediocre efficiency rating.

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For better samples - go here:

https://photos.google.com/share/AF1QipM1nZyQ2tRPrCSv6U9ylFio45nTMrLzoaCAQMWI1HBqsTObhriVSBbxQrF87_OVAA?key=M1A4bE52WGhQUnB6Q1VzZDJ5eHZEa1ZtM0E4UEN3

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And while we are at ranting - why does this lens cost $1500 and the near-identical Sigma costs $800?
Sure there's the economy of scale - but it's also a way to push a system into oblivion.

It actually is cheaper over here than the PL 100-400 is, while the PL 100-400 is several years old already.

If it really is the same as the Sigma, one could always get the Sigma with an adapter, I guess.
However, even if it is, it likely has some Oly sauce as well. I never had any focusing problems with Oly lenses, other than occasional focusing speed, mostly indoors with non-pro lenses, but I have always had problems with focusing Sigma lenses, to the degree that I will never buy another Sigma lens branded as Sigma.

Kind regards, Wim