Sigma Corporation has issued an advisory to Canon 40D owners using the company’s APO 120-400mm F4.5-5.6 DG OS HSM or APO 150-500mm F5-6.3 DG OS HSM lenses.
There’s a firmware defect that decreases the number of continuous frames per second when the Canon 40D digital SLR is in AI Servo AF mode, and the APO 120-400mm F4.5-5.6 DG OS HSM for Canon or APO 150-500mm F5-6.3 DG OS HSM for Canon lenses are attached to the camera with the OS function switched ON.
Sigma says they will fix this for free. There’s a free-upgrade service to their customers available at their website.
The lenses requiring update for EOS 40D camera are:
APO 120-400mm F4.5-5.6 DG OS HSM for Canon Serial Number lower than 1011001
APO 150-500mm F5-6.3 DG OS HSM for Canon Serial Number lower than 1007001
Except for the above serial numbers, the other lenses are fine.
[Site: Sigma]