Difference between Mamiya 645 120 and 220 inserts

paul ron · Apr 13, 2016

the difference is the frame metering mechanisms. the preasure plates MUST sit exactly the same since the emulsion side of the film has to sit on exactly the same film plane to be in agreement with the view screen.

cameras that require preasure plates to be flipped, actually engage different gearing to meter the frames appropriate for the film being used. the amount of movement in the preasure plates (when pushing in from the film plane) are exactly the same in both 120 and 220 in the rb67 and ETRS inserts. i havent measured a mamiya 645 or anything else, because I dont have any handy right now.

the extra wear is due to the additional stress on the gearing system.

John Koehrer · Apr 13, 2016

^^^The film is held at proper distance by the rails between the film and lens. Held at that point by a pressure plate that can't push the film any further forward so is aligned with the mirror
The stress on transport FOR PRACTICAL PURPOSES is of no consequence. How much film ya gonna shoot?
RE: revolving pressure plates. What camera has a linkage that affects gearing? Just curious.

paul ron · Apr 13, 2016

there are alot of tlrs n cameras that do that.

the wear someone mentioed he saw on the old mamiya site forums is actually the parts in the gearing to regulate the difference in 120 vs 220 roll diameter. there are extra force on the mechanisms.

Huss · May 16, 2016

So I was using my Fuji 690 III with 220 film. The pressure plate needs to be flipped over from 120 to 220. So obviously there is a difference otherwise why would Fuji do that?
In the instruction manual on page 8 it states:
"Be sure to set the film selector and pressure plate for the film (120 or 220) that you are using.
If you don't use the correct side of the pressure plate, you won't get precisely focused pictures because the film will not move into the exact focal plane.
(120 roll film is attached to an opaque backing paper over its entire length, but such paper is used only on the leading and trailing ends of 220 roll film. The thickness of the backing paper causes a shift in the position of the focal plane and the pressure plate adjusts for this difference while keeping the film flat on the focal plane at one and the same time"

And this is why Mamiya provides different inserts, with different pressure plate positions, for the Mamiya 645. Nothing to do with wear or extra forces. Just simply because the 220 film is thinner than the 120 film.

ITKI · Aug 9, 2016

MattKing said:
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.

This is good info, thank you.

Still, in Mamiya's M645 manual (page 27) it says:

Make absolutely sure to match the film insert with the film type being used.
If the wrong insert is being used, the correct film plane will not be maintained and optimum sharpness will not be archieved.

ambaker said:
Matt, my understanding is that if you remove the triangle, the counter sees the back as 120 and the counting would work correctly.

Indeed.
Mamiya cautions that when using the 220 insert with 120 film the leader paper might get caught up in the shutter,
though I guess that would only happen when the insert isn't "hacked" (triangle piece removed) and one would continue shooting and winding.

paul ron said:
the difference is the frame metering mechanisms. the preasure plates MUST sit exactly the same since the emulsion side of the film has to sit on exactly the same film plane to be in agreement with the view screen.

No, due to the 220's plates having that little step / recess, the whole shebang, pressure plate and film, gets a bit closer to the lens.
Look at the recesses, and at the rails inside the camera. It's pretty self-explanatory; it's levelling out the thickness of the missing backing paper.

paul ron said:
cameras that require preasure plates to be flipped, actually engage different gearing to meter the frames appropriate for the film being used.

Have never had one where the flipping engages different gearing, just thought of my Rolleicord, where adjusting the plate definitely does not engage any gearing, but adjusts height - for the missing backing paper when it's being used with 35mm film.

Could things actually be that simple?

darkroommike · Aug 9, 2016

The Mamiya camera registers the film on rails in the camera (or back) on the emulsion side of the unit. 120/220 backs for other cameras may or may not use a different registration system but anything that registers on the paper or the back of the film might have issues with differing film thicknesses. Most of the pressure plate flipping cameras I am familiar with use the different pressure plate position to change the counter.

The Mamiya system is rather elegant, remove one bit of plastic and change the counter. There's probably a bit of CYA in the Mamiya statement regarding wear on the pressure plate but if there were still medium format wedding shooters scrambling for a replacement for 220 it would probably be relevant, but for the way "we" all shoot the issue is moot. (It's a great day for me when I can use moot in a sentence.)

And if I did manage to run 1000 or 10,000 rolls of 120 through a camera and wear out a modified 220 holder I could flip and buy another 220 holder for $30-40 and modify the new 220 holder in the same way. It's more likely the camera (or the cameraman!) will wear out first.

ITKI · Aug 10, 2016

darkroommike said:
The Mamiya camera registers the film on rails in the camera (or back) on the emulsion side of the unit.

Sorry, but am not able to follow you.

Just put a roll of 120 in my 220 insert yesterday; film advance to the first frame definitely felt somewhat rough, but advance to the second frame pretty normal.

I guess the modified 220 inserts will wear out somewhat quicker, but as, you say: the issue is moot.

Only thing that concearns me is sharpness - will do a test shot wide open..

Don Madson · Oct 8, 2016

Luckless said:
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.

Deleted member 88956 · Apr 30, 2019

Just found this thread facing same question as I'm looking at a cheap 220 insert. Unfortunately I am now convinced this thread is parallel to Pentax 645 on same issue. The sole difference is that P645 is motor driven, thus ALWAYS exerting more load on the motor when 120 film is used in 220 insert. Mamiya is normally hand cranked so one can take things "easier" when advancing. However, it is funny to read all comments accusing Mamiya of BS regarding extra wear. Back when these cameras were new and under warranty, such use would void warranty on every piece linked to such use, so Mamiya had an obligation to state the warning. These days it is no longer a consideration.

So P465 and M645 can have 220 insert altered easily to fool camera's counter, but both have pretty much same plate design and both are NOT meant to be used with 120 film on 220. I'm sure it does work on both systems, just not as intended. All arguments are sort of valid, given limited use (not the old pro style many rolls a day) thus far lesser additional wear, but unless I'm in a dire need to use a 200, I see no reason to.

Difference between Mamiya 645 120 and 220 inserts

Deleted member 88956

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