Thank you for using Canon products.
Firmware Version 1.3.3 incorporates the following improvement and fix:
When updating the firmware of your camera, please first review the instructions thoroughly before downloading.
Once the EOS 5D Mark III camera is updated to Version 1.3.3, it cannot be restored to a previous firmware version (Versions 1.0.7 through 1.2.3).
This information is for residents of the United States and Puerto Rico only. If you do not reside in the USA or Puerto Rico, please contact the Canon Customer Support Center in your region.
Customer Support Operations
Canon U.S.A., Inc