|Thank you for using Canon products.
We have become aware of the following phenomenon that occurs during use of the Speedlite 600EX-RT and Speedlite Transmitter ST-E3-RT, which were released in March and April of 2012, respectively. The details of the phenomenon and Canon's service policy are described below.
We would like to offer our sincere apologies to users who have been inconvenienced by this issue. Moving forward, we will spare no effort in our quality management to make sure our customers can use our products with confidence.
We have determined that units do not operate normally in linked shooting with radio transmission and wireless flash shooting with radio transmission when 7 or more units are linked.
This phenomenon does not occur when 6 or fewer units are linked.
Speedlite 600EX-RT and Speedlite Transmitter ST-E3-RT
Units with a combination of 3rd and 4th digits in the serial number in the ranges shown below are affected.
However, even if the serial number is within the ranges above, the unit is NOT affected if there is a round, white dot at the top right of the battery compartment as shown in the photos below.
If you own one of the affected Speedlite 600EX-RT or Speedlite Transmitter ST-E3-RT and you would like us to update the firmware, please bring the products to your nearest Canon Service Center and we will update the firmware free of charge.
Should you have any questions about the announcement, please contact the Authorized Service Facility in your area or you may contact the Call Center within your region.