Difference between Mamiya 645 120 and 220 inserts

[Huss]

I use a 645 Pro TL, and have 120 and 220 inserts. The 220s are of little use to me since 99% of the film in my freezer is 120. I was going to buy some more 120 inserts when I found numerous threads claiming that the 120 and 220 are the same, the 200 just has a little triangular piece that allows the frame counter to go beyond 15.
Too good to be true, I could just remove that bit from my 220 inserts. But I then checked them carefully against my 120 inserts, and there is another difference. The position of the pressure plates are identical on both 220s, and a tiny bit recessed compared to both the 120 inserts. It is a slight but noticeable difference. The 120 pressure plate is essentially flush with the side rails, the 220 is lower than the side rails. This is one of those easy to see, hard to photograph items, but I gave it a go. See below (I tried to frame them identically)

The the plane of focus will be slightly different between the two, which may be apparent while shooting at large apertures. I wish it wasn't so, as I thought I was about to save me some money.

 

[Kirks518]

Are you sure you're not switching them around? I would think the 120 would be slightly lower to allow for the backing paper. I'll have a look at some of mine, and see if I have the same recesses as you.

 

[Kirks518]

Well, I just compared a 120 to a 220, and both of my pressure plates are perfectly flush with the edge of the rails. The only difference I see between them is the triangle-shaped piece.

 

[Huss]

Are you sure you're not switching them around? I would think the 120 would be slightly lower to allow for the backing paper. I'll have a look at some of mine, and see if I have the same recesses as you.

Nope, no switching them around. The 220s are both slightly recessed, the 120s are flush. It's how 'mine' are. Can't tell how other people's are. Kirk already says his aren't any different.

 

[jvo]

the pressure plates placement (thus pressure)are different for 120 vs. 220 to hold the film flat. i guess it's theoretically possible to modify the 220 for 120 film.

everything i've ever read in the instruction manuals and film loading procedures always emphasized the importance of this plate and it being able to hold the film properly on a flat plain. my impression is they've always cautioned about it's sensitivity and other horrors attendant upon tampering with or even touching, (something about the apocalypse and end of the world)!

having said that, i say go for it... there not doing any good sitting on your shelf. if you're handy, its' gonna cost you some time and a roll of film to test. the upside is, you may have discovered a new and profitable endeavor.

jvo

 

[Wayne]

I just spent 3 days reading about the purported differences or lack thereof between the 120 vs 220 RB67 inserts. FWIW, my conclusion (and of those who use them) is the 220 inserts work fine for 120 film, and I became so convinced of that I just bought a 220 holder. I suspect the same applies to the 645 but I don't own one of those.

 

[Nige]

As another data point... just looked at my 2 220's and a 120 (didn't pull out camera bag to check 2 other 120's) and other than one 220 missing a screw (shows I've never used it!) they look the same with the pressure plate sitting flush. As the plate is on springs, wouldn't that allow for different thickness film with or without backing?

 

[Kirks518]

Here's pics of one of my 120 inserts and 220 inserts side-by-side. I guess there is a miniscule difference in where the pressure plate sits, but it wasn't noticeable until I looked at the pics. Do I think it'll make a difference? No.

120 on the left, 220 on the right;

 

[summicron1]

You guys are talking about the pressure plates, and on other cameras such as Rollei I do know you switch the plate for 120 (paper backing) and 35mm (no backing) and perhaps you do that with 220 as well, but as I look at this image of two backs I also note that that the rollers visible on the righthand insert are thinner -- film with no paper backing (220) doesn't make as fat a roll on the takeup side and so must be compensated for either through the gearing or something else.

just a guess. I have no use for a 220 back and so have never bought one.

 

[Huss]

Here's pics of one of my 120 inserts and 220 inserts side-by-side. I guess there is a miniscule difference in where the pressure plate sits, but it wasn't noticeable until I looked at the pics. Do I think it'll make a difference? No.

120 on the left, 220 on the right;

Thanks for taking the trouble to post Kirk. That matches mine exactly which shows there is a difference between the two, and not just with mine. The difference may be 'minuscule' but if it didn't make a difference then why would Mamiya make them different if it didn't matter? I think that issues with focus would only show up shooting wide open at near subjects. Stopped down for landscapes I dont think there would be any difference. However, something to keep in mind for portrait sessions etc.

 

[jvo]

You guys are talking about the pressure plates, and on other cameras such as Rollei I do know you switch the plate for 120 (paper backing) and 35mm (no backing) and perhaps you do that with 220 as well, but as I look at this image of two backs I also note that that the rollers visible on the righthand insert are thinner -- film with no paper backing (220) doesn't make as fat a roll on the takeup side and so must be compensated for either through the gearing or something else.

just a guess. I have no use for a 220 back and so have never bought one.

a good point...

it occurs to me that there must be SOME sort of difference - on many TLR's the pressure plate gets slid up or down, or turned 90 degrees when you switch from 220 to 120 and vice versa. it can't only be to change the little icon to say 220/120... hmmm.

what ever difference it makes, i'm sure someones is gonna experiment - hope they'll post results!!!

jvo

 

[Huss]

a good point...

it occurs to me that there must be SOME sort of difference - on many TLR's the pressure plate gets slid up or down, or turned 90 degrees when you switch from 220 to 120 and vice versa. it can't only be to change the little icon to say 220/120... hmmm.

what ever difference it makes, i'm sure someones is gonna experiment - hope they'll post results!!!

jvo

Yup on my Fuji 690 I have to flip the pressure plate for 120 or 220.

 

[Kirks518]

I also see what summicron1 is saying, but the gears are the same size, and the same number of teeth (14 on the small gear, 20 on the large gear). There may be something inside the camera body that makes an adjustment to the internal gearing for the frame advance distance based on the insert being used? The (removable) triangle piece from the 220 insert is the only difference I can find between the two types. And all that the triangular piece does is flip a lever inside.

But, I just went through the repair manual, and I see no evidence of there being a different gearing for 120 or 220.

So, with that said, I may run a roll of 120 on the 220 insert just to see what happens.

 

[Luckless]

I just tried to take a measurement on my C330f in 120 and 220 settings with a micrometer out of curiosity on just what the difference was, but I honestly couldn't get a really reliable reading on what the value is due to the nature of the spring plate. (It would be trivial if I took the time to set up some clamps to hold the door and micrometer in place, but too much fumbling involved trying to hold everything and adjust it down to take a reading with only two hands to get a precise accurate reading before the back moves.)

But it was a rather nice reminder that they are pressure plates. They're on springs, or at least they are on any camera I've yet handled, and many of these old cameras are getting on up to 20-30 years old or more, so it shouldn't be surprising if the exact pressure and depth settings they offer are slipping from expected tolerance a little.


A random sampling of where the plate rests with regards to parts around it might not really tell you all that much in general anyway, because what really matters is where it rests when the system is under tension anyway. One back might have a slightly lighter over all spring with a hair longer travel, but as long as it settles back to its proper depth when the film is pulled across it then it really doesn't matter.

 

[Kirks518]

I looked a little harder at the two backs, and found 2 differences in the pressure plates.

1) on the 220, where the edge of the roll would be, the indents are circular, not diamond shaped
2) on the 220, the last row of indents (the circular ones) are lower then the rest of them

So them being lower accounts for what we are seeing in the above photos; the appearance that the 220 pressure plate is set 'lower' then the 120 pressure plate, when in fact, the face of the plate is at the same height. It's just that the indent makes the edge of the plate lower in relation to the rail of the insert. Why they are circular and not diamond shaped? Not a clue.

Macro of the edge of a 220 insert plate;

Arrow points to the 'lip' of the indent

The indent circled (you should be able to see the step):

 

[MattKing]

A very long time ago there used to be a Mamiya film camera forum hosted by Mamiya America. There was a FAQ section on that forum that talked about using 120 film in a 220 back or insert.

Essentially, the recommendation was that you could use 120 film in a 220 back or insert, but you could expect accelerated wear on the back, because the different setting of the pressure plate would both wear the springs more and wear the gearing more.

The plate has no affect on the plane of focus - that is determined by the rails. The plate does have an affect on how close the film is held to those rails. As 220 film is thinner (no backing paper where the images are) the plate pushes "harder" on the sandwich of 120 film and backing paper. The harder push increases the camera wear.

IMHO, the counter is the biggest reason not to use 120 in a 220 back. All it takes is to forget once and try to take a couple of important shots on what would be on frames 16 - 30 and you will realize what I mean.

 

[Kirks518]

The plate has no affect on the plane of focus - that is determined by the rails. The plate does have an affect on how close the film is held to those rails. As 220 film is thinner (no backing paper where the images are) the plate pushes "harder" on the sandwich of 120 film and backing paper. The harder push increases the camera wear.

I think that explains the 'indent' I mention above. It would allow the plate to push the film that much closer, as the indent will sit on the rails.

 

[Huss]

Kirk, I am really hoping that in use there is no difference between the two inserts. Just so I can convert the 220s to 120 use. If you get round to testing them, please shoot wide open close up (as that is where any discrepancies will be shown most clearly) and post here!

 

[Kirks518]

It may be a while. I only have one 220 insert, and I still have plenty of 220 film to run through it. But if I do, I'll let you know.

 

[ambaker]

Matt, my understanding is that if you remove the triangle, the counter sees the back as 120 and the counting would work correctly. If you put some 220 film in and did not replace the triangle, you would lose the last half of the roll. I have a number of both backs, but I also have 220 in the freezer so I have not yet converted any. I also have the 35mm back for the 645 and it works quite well. Originally I worried about sharpness with the medium format lens on 35mm film. But I am happy to say that the results were quite favorable. Now I carry the back as a backup, in case I run out of 120 film.

 

[pagonzales]

I use the older m645 bodies with no interchangeable backs. I believe they use the same inserts as the newer bodies. When I got my camera, it came with a 120 and a 220 insert that was already modified to use 120. When I got another 220 insert, I just removed the triangular piece to use 120 in it (just a screw if I remember correctly). All three inserts are indistinguishable in use and stop winding after 15 shots.

 

[Kirks518]

I use the older m645 bodies with no interchangeable backs. I believe they use the same inserts as the newer bodies. When I got my camera, it came with a 120 and a 220 insert that was already modified to use 120. When I got another 220 insert, I just removed the triangular piece to use 120 in it (just a screw if I remember correctly). All three inserts are indistinguishable in use and stop winding after 15 shots.

Is frame spacing consistent with the 220 inserts as well? Not that spacing should be an issue, there is almost an entire frame wasted at the end of the roll, but we were curious if the frame spacing is the same on both.

 

[pagonzales]

Frame spacing seems to be consistent across all three (120 and 2 converted 220) of my inserts. I forgot where I read it but I read somewhere that good frame spacing is one reason why the Mamiya m645 system only had 15 frames instead of 16 for other 645 systems.

 

[Huss]

After comparing to yet another 220 insert, all the 220s have the pressure plate at the same level, and all are equally different to the 120 inserts.
If there was no difference between the two in use, Mamiya would not make them differently..
So I picked up another 120 insert from Roberts camera for $20 including case. The cost of a roll of film with dev and scan is more than that, so it was not worth it to me to use a 220 insert knowing already that the dimensions are different.

 

[John Koehrer]

I think you're over thinking this. I also believe that Mamiyas statement about wear & pressure
on the mechanics is BS That's from a PRACTICAL standpoint. Over the lifetime of the back
I doubt that very few people here woulld ever get to that point.
I don't remember ANY thread on this site( I don't bother with others) that says any 220 back is incompatible with 120 film.
Bronica, Hasselblad, Fuji, Mamiya. The Proble(?) seems to be the backing paper introduces an error in counting
and depending on which brand, you may or may not lose a frame.