Mamiya C220 back pressure plate question

Hello gurus!

 

I've recently purchased a heavily used C220 and being a total beginner in medium format I am not sure if it is all functional. I haven't yet tried loading a film in it. There is a rotating pressure plate on the back cover, which has two positions: one for 120 film and another for 220. I can turn it with no problem but I don't understand what it changes except for the text in the indicator window. Could someone please explain what is it supposed to do?

 

Thanks.

220 film is thinner so the plate adjusts the pressure to keep the film flat^^

220 film is thinner so the plate adjusts the pressure to keep the film flat^^

Yes, but I can't see how it does it. There are two flat springs holding it, which in one position are parallel to the direction of the film and in another are perpendicular. I don't think this changes the pressure but perhaps when the springs are parallel to the movement of the film the plate can rock a little bit with the film movement. I am not sure if it makes sense though...

the rotating plate engages a different counting and frame metering system. it has nothing to do with pressure because the springs are preset.

the rotating plate engages a different counting and frame metering system. it has nothing to do with pressure because the springs are preset.

C220 has a separate knob for that!

so there's no reason to turn the plate?

 

what happens if you dont turn it?

so there's no reason to turn the plate?

 

what happens if you dont turn it?

Well, I don't know what will happen. Visually all that happens is the number 120 changes to 220 on the back and the red dot moves from 120 position to 220 position on the inside. And the direction of the springs under the plate changes as well. As I've said I haven't tried loading the film yet and I don't really want to ruin a film either...

The pressure plate sits on the outside rails in the camera when closed, the film sit against the inside rails. The outside rails are a little higher than the inside rails, such that the pressure plate creates a channel for the film. The size of the channel, along with the curl on the film allows it to sit flat. 220 film requires a narrower channel, so when you rotate the pressure plate, you will notice that the edge of the plate (that sits against the outside rails when closed) is machined down a bit, resulting in a narrower channel for the film.

when you rotate the pressure plate, you will notice that the edge of the plate (that sits against the outside rails when closed) is machined down a bit, resulting in a narrower channel for the film.

 

Hmm, I haven't noticed that but I will check later today...

that ensures film flatness.

 

you will love this camera.