Canon EOS-1Ds Mark III Firmware Version 1.2.2
Canon has posted a firmware update for its EOS-1Ds Mark III full-frame digital SLR camera. Version 1.2.2 enables focusing with the central AF sensor when the camera is used with the EF 200-400mm F4L USM Extender 1.4X lens and teleconverter whose combined maximum aperture is f/8. You can download the firmware upgrade from the website below.
Website: Canon EOS-1Ds Mark III Support