Sigma says its lenses are not compatible with the new Sony SLT-α33 and SLT-α55 ‘translucent mirror’ cameras. Sigma’s lenses for the Sony mount may have a potential aperture operation problem when used with these new interchangeable lens digital cameras.
For those who may have bought the Sigma lenses for use with the α33 and α55, Sigma is offering a modification service free of charge. They assure that future production of Sigma lenses will be fully compatible with these cameras.
The free modification service is offered for currently produced Sigma lenses and not for discontinued lenses. See your nearest Sigma service station if you are affected by this issue.
[Site: Sigma Japan]