[mike]

Well, it's made in JP - probably because it's made or at least pre-assembled by Sigma?

I'd say the lens is alright - it's just the price tag and the poor IS implementation that I don't understand.

Also - you can use an EF-MFT AF adapter to mount such FF lenses. If I had the choice between this one and a Canon EF 70-300L IS with adapter (costing the same), I'd probably settle for the Canon lens.

I looked into ef-mft af adapters because a couple of my canon lenses weren't stolen, it hurt my head trying to figure out which lenses work and don't. These seem very plug-and-pray.

[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

[Klaus]

If the Olympus 100-400 is really a Sigma design (as I've heard loads of times already) does that mean it's an FF lens in disguise?

Yes.  The design schema is identical to this one:

https://www.sigma-global.com/en/lenses/c..._400_5_63/

The dimensions and weight also match - plus-minus a little due to the "extended" tube and Oly styling.

FWIW, it's not the first outsourced lens - the Olympus 75mm f/1.8 is also based on a Sigma patent it seems.

Cooperations between manufacturers aren't unusual anyway. Think of Tamron/Tokina & Pentax.

And Tamron has been "known" to do designs for Sony I think. There are also rumors that the Batis lenses are made by Tamron.

[Brightcolours]

Especially a few years ago Tamron made some Sony lenses. Sony has or had a stake in Tamron. Tamron has made the AF film era Nikkor 70-300mm lenses too.

About the Olympus 100-400mm: It is clearly similar to the Sigma. The lens construction is similar, but not the same. Some lens elements/groups have a slightly different shape, and the back elements/groups are smaller (so that means that the lens is not an FF lens in disguise).

https://www.isolapse.com/wp-content/uploads/2020/08/M.ZUIKO-DIGITAL-ED-100-400mm-F5.0-6.3-IS-800x445.jpg

With tele lenses, the front elements are usually not smaller for APS-C and MFT compared to FF, when the max. aperture is the same, as the max. aperture is about the same size as the aperture itself. The aperture size is the opening as seen through the front of the lens. So, it makes sense that the front elements are the same size, and it is the back elements that have been shrunk because they only have to cover MFT sensor size.