EOS R6 Mark II, 600EX RT, ST-E3-RT - Trouble getting high speed sync

[danikatz]

Hi.  I'm trying to use this combination of equipment to take a photo in high speed sync. I set my ST-E3-RT transmitter to radio master and the 600ex to radio slave. I put the transmitter on high speed sync.  However, the ability to put the flash into high speed sync goes away when I connect the 2 devices as master and slave.  The "sync" option in the menu disappears from all menus.  When I go to take the picture, the camera won't allow me to go beyond 1/200th shutter speed.  And no, the camera is not on the "lock" setting with the power button.  If I set the camera first to a high shutter speed such as 1/1000 and then turn on the transmitter, it looks like the camera is going to take the picture at a higher shutter speed but then it reverts back to 1/200th when I depress the shutter.  I am using a mechanical shutter.  Any ideas on what I need to do differently?  Or are my items incompatible?  My ST-E3-RT is the first variation. It's barely used but it is older technology.  I'd love your help!  Thanks!

[John_Q]

Hello danikatz,

Is the ST-E3-RT directly on the camera hotshoe? This item or the Speedlite 600EX-RT cannot be used that way. You would need to use the Multi-Function Shoe adapter AD-E1 on the hotshoe and place the transmitter in that.

[p4pictures]

High Speed Sync is not supported with the original Speedlite Transmitter ST-E3-RT, you need to use the ver2 to enable it.

Check with your local Canon service centre as there was a possibility to have ver1 / original model ST-E3-RT transmitters updated with ver2 functionality for a small fee. I know this is true as I did have my ST-E3-RT v1 from 2012 updated by Canon UK and it is not working correctly as a ver2. 

[rs-eos]

I used to own the first version of the ST-E3-RT transmitter along with several 600-EX-RT units and HSS was indeed available.

[p4pictures]

You are correct. I read HSS as 2nd curtain sync, my mistake and apologies

[p4pictures]

Can you check the Slow synchro setting in your camera?

Go to External Speedlite control menu, on third page of the red menus and press SET. Then look down for the Slow synchro setting. If it shows 1/200 then this is the setting that is blocking the high speed sync, but it only applies when you have the mode dial set to Av or P modes. There is a caution in the EOS R6 Mark II manual about this.