Can you please tell me how many sprockets per frame of 6x6? I can only guess as I've never shot any perforated 70mm.[/QUOTE]
No, sorry, can't help. My interest was aroused by the sheer mention of 70mm.
Having just got my EL/M back into commission, I found 70mm backs available at silly prices compared with A12's, but my subsequent search for film proved negative and so I abandoned my intended project. Ideally, I would like colour reversal film, perhaps I will have to be content with regular magazine changes.
I'm into painting with light - NOT painting by numbers!
Should be the same as Imax Film images;
"65/70mm film has about 64 perfs per foot, same as 35mm.
So 15 perf frames come at 4.267 per foot.
Strictly speaking, the perf pitch (like 35mm) is 0.1870 inches, so there are 64.17 perfs in a foot, and therefore 4.278 frames per foot."
See here: http://www.cinematography.net/IMAX15...mTechSpecs.htm
Warning! Some digt@l content!
Just a follow-up to those who are interested:
I finally got my hands on a Mamiya RB Pro-S handbook, and they list the holder as capable of taking 55 frames of 70mm full-frame (~13 feet/3.9m). However, the counter goes up to 65 frames, which leads me to believe that it is capable of taking 65 frames with a 16-foot/4.86m load, leaving maybe 3 frames worth of leader.
So this is cramming an extra foot into the cassette over what people normally say they can fit in at the max, but since it is just leader, it is lost anyway, and can, as such be threaded into the other cassette. I'll need to test to make sure the final three frames will fit into the take-up cassette, especially without scratching, but this is much better than 50 some have said was the maximum amount of film exposures, although it isn't the 70 exposures I'd hoped for, which would have required 17 feet/5.2m of film, and another five increments on the film counter, although I guess it'd still be doable if I loaded the 70mm film in the mag without protective cassettes, which requires me to have at least a half-dozen 70mm cassettes at my disposal, since it'd be impractical to change one in a dark bag every 70 shots.
Anyway, 65 shots allows me to shoot 3 1/4 times as much film without reloading, almost as much as shooting in RAW+JPG Basic on some DSLRs with a 1 gig memory card. Cool!