Differences between 120 and 220 film inserts

[ian_rose]

<p>I thought I would post this so people with old Mamiya 645 220 film inserts can see what the differences are between them<br>

While All the time I keep seeing people say the spring rates are different for the film pressure plate.<br>

I checked my parts book for the differences the only difference is shown in the image below and the only difference between the pressure plates is that the 220 one that I compared to a 120 one was that the leading edge was more radiused and polished. I can supply PDF if anybody would like them.<br>

Ian R</p><div></div>

[rodeo_joe1]

<p>I'm pretty sure that the pressure plates have another difference, with a slightly deeper side lip on the 220 plate to take up the difference in thickness between 120 and 220 film. I wouldn't expect any noticeable difference in spring pressure, although some makes of camera used a reversible plate for 120/220. These had slightly more relief on the springs for 120 use, presumably to reduce frictional drag on the paper backing of 120 film, more than anything else.</p>

<p>The Pentacon 6 made no distinction at all between 120 and 220 film. The only difference was that the film counter could be manually persuaded to count to 24 instead of 12.</p>

[ian_rose]

<p>Joe Both plates are completly flat with no relief. My take on it was that the rad on the 220 insert is to stop it scratching the film where as the 120 insert the plate is just a punched out piece and you can still see the giloteen marks where the metal was sheared. then both are painted in gloss black. I have 1 new 220 insert with the plate removed that I use for 120 (got the 220 when Vistek Canada was clearing out ther old stock for 15$ also picked up some rear lens caps for 3$ each)<br>

Ian R</p>

[q.g._de_bakker]

Once more unto the breach, dear friends, once more...<br><br>Pressure plates apply pressure. They push.<br>Pressure plates that are thrown by the slight increase in thickness between 120 and 220 film are rubbish. But they aren't: there's plenty spring in them to cope with all sorts. Cameras that have 'switchable' pressure plates don't change the pressure plate, but toggle the frame spacing/counter mechanism.<br>In short: pressure plates do not have to be different "to take up the difference between 120 and 220 film".

[ian_rose]

<p>QG Exatly so if other members remove part SLS42131 Which is the trip for the frame counter and use for 120 film</p>

<p>Ian R</p>

[rodeo_joe1]

<p>Q.G. Is there nothing you won't argue about without knowing the facts?<br /> Below is a side-by-side picture of two Mamiya 645 inserts, one for 220 film and the other for 120. You can clearly see the recessed lip on the 220 insert's pressure plate, which is totally absent on the 120 insert.</p>

<p>In addition the Kowa 6 and 66 cameras had a reversible pressure plate that was totally uncoupled to the film counter. The counter had to be manually changed from 12 to 24 frames, as well as reversing the plate. I believe the Yashica 124 uses a similar system, although I've now sold the one I used to own.</p>

<p>Ian. If you'd bothered to actually look at the inserts, instead of working from a repair manual drawing, you'd have seen the clear difference. What's more, the diagram you've posted actually shows the rebate on the 220 pressure plate!</p><div></div>

[q.g._de_bakker]

R.J.<br><br>Is there nothing you would not take issue with, regardless of... well... anything? ;-)<br><br><i>"pressure plates do not have to be different "to take up the difference between 120 and 220 film"."</i><br>And that's hard fact.

[rodeo_joe1]

<p>On further reflection and examination of the camera, I think the lip serves another purpose than simply allowing for thickness differences between the two types of film. I believe it's there to keep 220 film between the guide channels either side of the camera gate. The backing paper of 120 film is slightly wider than the film, and so runs over the guides while pushing the film into the channel. 220 film has no such automatic guidance and needs a shaped pressure plate to perform the same function. Without it, it might be possible for 220 film to ride to one side and creep out of the light-tight paper trailer.</p>

<p>And Q.G. I'm just trying to get the facts straight here. There's far too much misinformation on the web as it is.</p>