The SX70 has a neutral density filter in front the the electric eye, held in by a ring. The ring can be pried out, the filter removed. That gives 1 stop, then use the L/D control for the second stop. If you have a Polatronic 2350 and the 1.5x Telephoto: the follow-flash will put in the 1-stop for you. I used a Polaroid Sonar with the flash, Telephoto lens, and 600 film for years. Keep a film cover to get the 600 film past the film chamber- the SX70 body is keyed to not load 600 cartridges.