My present understanding (primarily based on discussion board posts and my very own examination of photographs of the R3 shoe, ST-E10 base, 1D X shoe and bases of present sealed and non-sealed flashes that I’ve in hand, however topic to alter) is that you need to use the ST-E3-RT instantly on the R3, however the mixture is not going to be climate sealed. Should you use the AD-E1 shoe adapter (or the ST-E10), you may have a weather-sealed mixture.
Personally, I’ve an ST-E3-RT, 4 600EX-RT flashes, together with a 270EX II and MT24-EX. FWIW, I preordered each the ST-E10 and the AD-E1 adapter, however that was earlier than I had the piece of knowledge from Canon that non-sealed flash items can mount instantly on the R3. I am going to in all probability cancel/return AD-E1 as soon as it is confirmed that direct mounting of sealed flashes on the R3 works (I’ve by no means used a flash within the rain), however I am going to in all probability hold the ST-E10 – I just like the smaller dimension, and I’m used to controlling the flashes by way of the digicam menus quite than the controls/LCD on the ST-E3-RT.
