I’ve never considered using the flash with an open shutter on SX-70 (even though I advocated for doing this on other cameras: analog.cafe/r/a-simple-gui…).
I figure the darkness forced your SX-70 to open the shutter to 𝒇8 and you could probably use your flash’s guide number to get the exposure just right? That’s what I want to do now. 😁
Dmitri Sep 28, ‘23