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.