Canon has released a new firmware update for the EOS-1D X DSLR, version 1.2.1.
Firmware Version 1.2.1 for the EOS-1D X incorporates the following improvements and fixes:
The function to disable the Image size selection button has been added.
Fixes a phenomenon in which Err 70 and Err 80 may occur in very rare instances depending on the camera settings or shooting scene.
* The version 1.2.1 firmware being released this time is for EOS-1D X cameras with firmware up to version 1.1.1. If your camera's firmware is already version 1.2.1, it is not necessary to update the firmware. Please remember to read all of the instructions carefully before downloading the firmware.
To download and for more information, visit the Canon Download Centre website