I have 2 new 600EX flashes to go with my 60D. In reading the manual, it says you cannot use the flashes off-camera in RT mode with HSS. I didn't want to believe that so kept playing with things. It appears I may have found a way to do it but I want to know if anyone else has tried this. I went into the camera menu under Flash Control, selected the External Flash Func Setting option and changed the Shutter sync to Hi-speed. I have one 600 mounted on-camera and set to Master and one 600 off-camera set as slave using RT. I was able to use shutter speed > 250. Please lmk if anyone else has done this and if it worked for them. Thanks!
RT is capable of HSS for cameras produced in 2012. HSS is not capable with cameras produced before 2012 .
Most cameras produced before 2012 are ETTL capable but sync speed is 1 increment slower. Example - both my 5D3 and previously owned 5D2 sync speeds were 1/200. In RT mode my 5D3's sync speed is 1/200 while my 5D2 would have been 1/100.
Page 51 lists cameras that are not RT / ETTL capable.
I've seen the same statements and also found that even using radio mode you can set the high speed sync from the camera menu in my case on a 7D.
In fact I wrote a whole great article on all the things you "can't do with a pre-2012 EOS" and how some of them do indeed seem to work at least when you only have a couple of slaves. I've also recenlty discovered something that the old cameras can do with pulsed light off-camera flash but can't do with radio flash too...
Brian / p4pictures