Firmware Version 1.2.1 incorporates the following improvements and fixes.

• Extends the timing at which the high temperature warning indicator is displayed and the timing of automatic shut down of the camera due to a rise in internal temperature during Live View or EOS Movie functions.
• Optimizes program shift when the ISO setting of the camera is set to AUTO.
• Corrects a misspelling in the French-language menu.
• Corrects a phenomenon in which vertical magenta-colored banding appears in still images taken in movie-shooting mode. (This only occurs when in Manual exposure mode and when the ISO speed is set to "H". Note that this phenomenon only affects units with Firmware Version 1.2.0)

Firmware Version 1.2.1 is for cameras with firmware up to version 1.2.0. If the camera's firmware is already version 1.2.1, it is not necessary to update the firmware.
Note that cameras with firmware Version 1.2.1, 1.2.0 cannot be downgraded to a previous firmware version (such as Version 1.1.0).