Firmware Version 1.0.9 incorporates the following fix.
Fixes a phenomenon, in rare cases, the IS mechanism may cause the image to jump.
Firmware Version 1.0.9 is for lenses with Firmware Version 1.0.8 or earlier. If the lens’ firmware is already Version 1.0.9, it is not necessary to update the firmware.
The lens’ firmware version can be checked from the camera’s menu.
Preparations for the Firmware Update:
In the folder for the firmware you downloaded are instructions on the firmware update procedures (a PDF file in five languages: Japanese, English, French, Spanish, and Simplified Chinese). Before starting the firmware update operations, please be sure to carefully confirm your understanding of these instructions.
◆EF400mm F4 DO IS II USM
File name：EF007109.lfu /File size：1,441,844 bytes