Firmware Version 1.1.0 incorporates the following fixes and enhancements:
1. Wireless communication stability has been improved.
If the camera's firmware is already Version 1.2.0, it is not necessary to update the firmware.
Q&A Section:
Preparations for the firmware update:
In the folder you downloaded are the firmware (EL512000.CFU / file size: 648652 bytes) and 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 review the instructions to confirm your understanding of the firmware update procedures.
Firmware download link:
https://www.canon.com.au/speedlite-flashes/speedlite-el-5/support?option=drivers