I have a Sigma Flash gifted to me by a friend along with an EOS 600D (T3i) when he moved out of country and had no room for it. The issue is that my camera does not recognize it as compatible. I can only adjust the compensation settings. It is not listed on the compatibility chart of Sigma, as it only goes up to 500D for this flash on their website. However, one would think that since the camera is newer, it should probably then at least be able to use it.. more than TTL with only compensation adjustments, or manual mode, with no adjustments possible at all.. This leads me to suspect that it might in fact not be for Canon at all. The issue though: I have no clue how to tell, as this model have the same name for all brands.. and there was no box included from my friend. So, is there any way to be certain? I attached some images..