645 Film insert question?

Hi
Thinking of buying a 645 and I wondered if it matters which film insert it comes with. Can you put a 120 film in the 220 insert ok or is it important to have the matching film?

220 is just a longer roll of 120 (so you can squeeze more shots on). It's important to have the right back for the reel as they'll have take-up spools of differing widths and different gearings to accomodate a particular length - put the wrong one in and you'll end up with either overlapping frames or ones so widely spaced you'll lose shots.

Try and stick with 120 as it's much easier to get hold of.

Thanks for that. I realised that the 220 was just longer but was unsure if it was a problem, I forgot the spool is a diferent size.

Any idea what sort of money the 645n might go for, with a 75mm and the insert?

No idea - it depends so much on condition. Probably worth about £5-600 for a really nice one but you could get lucky for less, it does happen

Sorry to correct anyone, but it's not different spool widths that cause the problem.

120 and 220 film are on the same spool. The difference is that 120 film has backing paper the full length. 220 film only has backing paper at the start and end, this making room for more film length.

The upshot of this is that for 220 the film pressure plate has to be in a slightly different position, otherwise the images would be unsharp as the film would be outside the area covered by depth of focus.

In TLRs that take both 120 and 220 the pressure plate has to be rotated into a new position depending on the film in use. In the 645 it's a different film insert.

I always wondered why you had to do that and 30 years later I find out. Thanks you John.