Had this sent to me via a EOS news letter and thought Id pass on the info: When the EOS 40D is in AI Servo AF mode, and the - Sigma APO 120-400mm F4.5-5.6 DG OS HSM or - Sigma APO 150-500mm F5-6.3 DG OS HSM Canon-fit lenses are attached with the OS function switched ON, the number of continuous frames per second will decrease. To overcome this, Sigma is offering a free upgrade service. The problem only affects 120-400mm lenses with a serial number lower than 1011001 and 150-500mm lenses with a serial number lower than 1007001. Later lenses have already had their firmware upgraded.
that is one of the main reasons that i was hesitant to go with a 3rd party lens. thankfully my 120-400 works wonderfully with my 5d. have i mentioned before that i LOVE this lens?
