Greetings and a good question. I also have the Bronica ETRSI and the RB67setup and interested in a digital back. For the RB if you go
here , Mamiya states for the ZD back should happen late 2007/early 2008. For the Bronnie, I have not found anything yet. My local photo shop here in German has Leaf backs for the RZ67 series for rent about 200 bucks a day.
Hi Frank, love your work!