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Firmware version 1.2.3 incorporates the following fixes.

Fixes a phenomenon in which the settings of the Speedlite Transmitter ST-E2 revert to the default settings when both the camera and the ST-E2 are set to auto power off.
Fixes a phenomenon in which the Macro Ring Lite (MR-14EX, MT24-EX) and slave flashes do not sync while shooting wirelessly.
Firmware version 1.2.3 is for cameras with firmware up to Version 1.2.2. If the camera's firmware is already Version 1.2.3, it is not necessary to update the firmware.

Addition:
Note that cameras with the version 1.2.3 firmware (and also versions 1.2.0 through 1.2.2) cannot be downgraded to a previous firmware version (such as version 1.1.0 or earlier).


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Firmware version 1.0.9 incorporates the following fixes.

Fixes a phenomenon in which tone jumps become noticeable in some images, depending on the shooting scene, when shooting with the Auto Lighting Optimizer settings (Low / Standard / Strong).
Firmware version 1.0.9 is for cameras with firmware up to Version 1.0.8. If the camera's firmware is already Version 1.0.9, it is not necessary to update the firmware.

Before downloading the firmware update, please be sure to read the entire contents of this page.