Recently I contacted Olympus Technical Support regarding the movement of the lens mount of my M.Zuiko 100-400 zoom. I received permission to publish the official response that I received  from Olympus Americas which provides 100-400 mount clarification.

Here is the verbatim reply that I received from Olympus Americas:

Dear Thomas,

Thank you for contacting Olympus Technical Support.

This is normal for this lens. It is intentionally designed differently and the movement you see does not affect image quality or weather sealing.

Here is the official answer.

• That is not design mistake nor manufacturing mistake.
• In order to achieve smooth attachment and detachment of this lens, the size of the hole to fix the lens, which can be seen on the back of the lens, is designed slightly bigger than a hole on a camera mount. And the hole size of the 100-400 mm lens is also within our standard. Because of this, when rotating a zoom ring and a focus ring, the lens might move a bit.
• This does not affect the image quality or dust/splash-proof performance. Users can use this lens without any concerns.

If you require additional assistance, please reply to this email leaving the complete history intact.

Best Regards,
Bob
Olympus Technical Support
Olympus America Inc.

I know that some of our readers have purchased the M.Zuiko 100-400 mm f/5-6.3 IS zoom lens. If any of our readers were concerned, or were wondering about a slight movement in the mount of their lenses, I thought this official statement from Olympus Americas which provides 100-400 mount clarification, would be of interest.

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