See the full details in Sigma’s statement below.
Sigma’s lenses for Sony mount may have a potential aperture operation problem when used with the Sony α33 and α55 Interchangeable Lens digital cameras.
To overcome this issue, we will be offering, free of charge, a modification service to our customers who have purchased a Sony α33 and α55 and own Sigma lenses for Sony mount.
This phenomenon will only occur with Sony α33 and α55 cameras. Future production of Sigma lenses will be fully compatible with these cameras.
We deeply apologize for any inconvenience caused to our customers.
When shooting with a Sony α33 and α55 cameras, the aperture may not work properly and a “camera error” message will be displayed on the camera.
[Lenses requiring the modification]
All current Sigma’s lenses for Sony mount.
* For lenses discontinued several years ago, a modification may not be available. For further details, please contact your nearest authorized Sigma Service Station.
[Support for this issue]
We will be offering a modification service for our current range of lenses free of charge. Please contact your nearest authorized Sigma Service Station.