Forgive me if I've misinterpreted, but I don't think the biggest problem here is running 120 film through a 220 insert+back, or vice versa. The OP is proposing to buy an ETR (6x4.5) insert and run it through a SQ-A back made to handle 6x6 film. I'll admit to only having one of the systems (the 645) so I could be very wrong, but I would imagine that said mismatch is not going to align properly. Width-wise, maybe, but do they match top to bottom?
They do not match.
I do use a digital device in my photographic pursuits when necessary.
When someone rags on me for using film, I use a middle digit, upraised.
wiltw: Thanks for that, I hardly thought about it, I guess it must've slipped my mind. And thanks very much for measuring the different start film position for both 120 & 220 film..great help.
ignatiu5: Dohh (slaps forehead). Yet another thing that I missed completely. Guess the bottom line is that it won't work eh?
Well, here I go searching for a 120 SQ-A that's priced reasonably. Not that I have an SQ-A, lost out on it on fleabay, lost out on a lot of things these past few days...oh well..sigh...
You can run 120 film through an SQ-A 220 back just fine. The spacing might be slightly off, but you will fit all 12 shots on a roll. I haven't even had to move the start point. "Shoot" atleast to shot 15 before you open the back to unload the roll.
ive run 2 120 rolls through a 220 back on my bronicas. the first was a SQ-AM and the motor kept winding, but didnt advance the film past frame 9, so wasted film. the second through my SQ-A and hand cranking worked fine, but it did take a lot of effort later in the roll, which i found a little scary in terms of potential wear and tear on the gears.