Using 120 film in 220 back

<p>Hi all...forgive if the question has already been asked.....a friend has just picked up a mint condition Contax 645...with 2 film backs. 1 is for 120 film..the other is for 220 film. Wanted to know if he can use 120 film in the 220 back...as he has loaded a roll but the camera refuses to function...and yes he has turn it on.<br>

Any thoughts would greatly be appreciated.</p>

<p>Regards</p>

<p>Artur</p>

<p>On the <a href="/classic-cameras-forum/00YatJ">Rapid Omega 100</a>, 120 film will work in a 220 back, if a little awkwardly; but this is probably specific to each brand/make of backs. 120 film is thicker than 220, BTW.</p>

<p>220 film has a paper leader and tail but no paper to cover the film. <br>

The backing paper used on 120 film is .006 inch/.15 millimeters thick.<br>

120 and 220 film is 3.5 to 4.5 mil thick (.0035 inch/.088 mm-.0045 inch/.114 mm) thick depending on manufacturer and film type.</p>

<p> </p>

<p>Hi Artur. The Contax 645 should function with 120 film loaded in a 220 back. As Charles implied, the only difference in the back is that the pressure plate is set ever so slightly differently due to the fact that without the backing paper, the focal plane will lie slightly further from the lens for 220 film.</p>

<p>The camera has no way of knowing that you have 120 vs. 220 film loaded. In fact, on the "120 back" (really a 120/220 back) you can rotate the pressure plate around (that's the shiny flat part that the film lies next to) so that the arrow indicates either 120 or 220. The difference as I mentioned is to account for the slightly greater thickness of 120 film due to the backing paper.</p>

<p>There is some debate over whether or not this difference really matters. Certainly, if you are focusing things tack-sharp with a really wide-open aperture, the focus might be a little bit off if you have 120 film in a back set to 220. But if your depth of field is great enough, perhaps that will cover the difference.</p>

<p>But again, the camera doesn't know what's loaded (it trusts what setting you turn the arrow to, or in the case of the 220-specific vacuum back, it always assumes 220). So if you have 120 in a 220 back, it will expect to have 32 exposures available, when in fact your 120 film only holds 16. In this case, just shoot like normal for 16 shots, then fire off the rest until you hear the film flap around loosely inside...maybe that's 8 more shots or so? Obviously there is no actual film left, just backing paper, so you're not wasting film. If on the other hand you had 220 loaded in a 120 holder, it would get to 16 exp and then spin forward to the end of the roll—though there will be extra length involved so I don't know if it'll keep going to the very end or just leave you still in the middle of the 220 roll. You'd know if it got to the end because you'd hear the film flapping a couple times.</p>

<p>BUT your question was really "why isn't the camera functioning when loaded?" Since your friend is new to the camera perhaps he hasn't quite figured out everything to keep on top of. Some quick things to check:</p>

<ul>

<li>I assume you've tried brand new batteries; do you see any readouts at all in the viewfinder?</li>

<li>The main thing I wonder about is whether he's removed the dark slide. There's a little grey handle that sticks out the left side between the camera body and the front of the magazine; as a safety measure, the shutter will not fire if that's not removed, because obviously no film would get exposed while that's in place. Sometimes I'll be distracted by everything that's going on and forget about the slide after loading a new magazine, and it'll be a few minutes before I realize, "oh yeah, duh. Pull the dark slide out."</li>

<li>How is the film speed set on the side of the magazine? If your friend has the speed set to "—" instead of the actual number (400, 160, whatever), the camera automatically sets the speed based on a bar code printed at the beginning of the film roll. If the bar code indicates that 120 film is in a 220 magazine, the camera won't work and 120 then 220 will blink on and off in the viewfinder. You could probably fix this by turning the camera off and setting the film speed dial manually.</li>

</ul>

<p>Finally, you could just go into a bathroom with the camera, put a towel at the bottom of the door, open the film magazine and snap open the film spools so that you can wind the film tight again. Then turn on the lights and do it right: put it on the 120 back. And now that I've typed all this, that's probably the best thing to do anyway, although I do see it's a few days later so maybe he's figured it out by now. Incidentally, there's not a lot of film available in 220 these days; mostly Kodak Portra I think for the few wedding folks left on film.</p>

<i>"[...] the fact that without the backing paper, the focal plane will lie slightly further from the lens for 220 film."</i><br><br>Is not a "fact", but on the contrary, completely incorrect. There is no debate over this: it's a very simple, clear matter.<br>The focal plane is and remains where it is, no matter how thick the film + paper or film only pack. The front of that pack - the emulsion side of the film - will be in the correct position (set by surfaces on either side of the film gate, and pushed there by the pressure supplied by the pressure plate) no matter how thick the film or film + paper.<br><br>Pressure plates do not need to be adjustable. (There may be some debate - confusion, rather, fueled by the 'adjustable' plates that are found in some cameras) over this, but again: it's a very simple matter. There is no need for adjustable pressure plates at all.) All they need to do is provide enough pressure to push the film into the correct position.<br><br>What needs to be done is set the transport mechanism so it produces correct film spacing. Wrapping the thicker 120 film + paper pack increases the diameter of the take up spool faster than wrapping the thinner 220 round the spool film does, so it takes less rotations of the take up spool to transport the film over the same distance. The transport mechanism must be switched over to 120 or 220 'mode'.<br>Those 'adjustable' plates are switches.

<p>Thanks, Q.G., for clarifying some of my points, though now <em>I'm</em> a little confused. I certainly wasn't clear about the "focal plane," since that refers to the optical spot in the camera where the light focuses, and which would always be the same regardless of what is or isn't loaded.</p>

<p>As far as adjustable plates go, I looked in my Contax manual before responding to Artur above and it does state that one of the problems caused by incorrect setting of the pressure plate is film "out of focus." I understand what you're saying about the plate only needing to exert the right pressure to push the film forward against the frame in the camera, but wouldn't manufacturers understand this? And mightn't a back set at 220 exert slightly <em>too much</em> pressure forward that could create excessive friction on 120 film with paper backing that would needlessly stress the transport mechanism or motor?</p>

<p>I'd never thought about frame spacing as you mention, but that makes total sense. So is this true for all cameras? Does every single camera using any sort of roll film (35mm, 6x6 TLR) adjust its film advance mechanism as the roll progresses from the first to the final frame to account for the greater thickness of film on the takeup spool?</p>

<p>(Of course, this all begs the question that without the [220] vacuum back on the Contax, 120 film is sometimes out of focus anyway allegedly due to having sat too long tightly curled up or something. I think the reason may be in question, but I've personally seen it: photos with several objects across the frame, at the same focal distance, out of focus for about 1/3 of the frame at the edges but OK in the middle, as if some sort of tilt/shift had been used.)</p>

Some manufacturers do, some don't, Skip.<br>Some maunfacturers design a small channel the film runs through. The pressure plate doesn't push the film, merely keeps in the channel. The depth of the channel is then fine-tuned to the (expected) thickness of the film or film + paper pack. Though not uncommon, that's not the way to do it. Quie simply because it does not put the film quite where it should be. It only ensures that it is somewhere in the proximity of where it should be.<br>The way to do it is the way many (think outside the MF realm as well) other manufacturers do it: have a precisely machined surface that forms/represents the plane where the emulsion has to be, and a pressure plate that has enough spring to it to press (!) the film against that surface. There is no need to have a channel for the film to move freely in/through, because the pressure needed to push the film into position is such that no matter how thick the film or film + paper pack is, it will move without a problem. So why that channel?<br><br>There are three sorts of transport mechanism: one that measures the length of film that is transported, which is easy to do accurately if the film has sprocket holes (or other easily detected or usable marks at precise, regular intervals). Neither 120 nor 220 film has sprocket holes or other usefull markers.<br>Another sort is one in which the number of revolutions of the take up spool (the spool that is driven - through gears - by the transport crank) it takes to transport a given length of film is 'preprogrammed'. With the diameter of the take up spool increasing as film is wound on it, it takes progressively fewer turns to wind a iven length of film on the spool.<br>Many cameras that use film without sprocket holes use this type of transport mechanism, but there are also cameras that use a feeler roller, that relies on friction between it and the film to be turned by the moving film. A given length of film moving below that roller will always result in the same number of rotations of the friction roller, so counting those will give a measure for the length of film transported.<br>If sprocket holes are available, using those is best. If not either other method will work, with the friction roller being independent of assumptions about film or film+paper thickness. But slippage can mess things up. But both these methods work well.<br><br>But no matter what method is used: the mechanism has to be told what sort of film it is transporting, if only to know how many frames to allow before blocking.<br><br>Contax, 220 film and the vaccum back is... well... 'something else'.<br>Contax, famous for the (commercially unsuccesful) vacuum back in the RTS, decided that it would be a good marketing strategy to offer such a thing for 645 users too. So Zeiss (stakeholder in the Contax camera system and owner of the brand) published the results of a study they said they conducted that showed that 220 film was much flatter than 120 film, urging us all to use 220 film. 220 film is, of course, the only variant of the two that a vacuum back would work with.<br> Coincidence?<br>They also told us about the curl film acquires when left wrapped around a roller for a while. It will. But how big a problem is that? Remember (and this Zeiss did not point out) that film comes wrapped tightly around a small diameter spool for the longest time before we use it. Yet people use and have used roll film for ages and ages, without too many complaints. But still: a vacuum back could make a difference, yes.<br>But eventually, not many people recognized the problems Zeiss told us about as of a magnitude that would make continued use of the current cameras an impossibility. So despite that all, the Contax vacuum back flopped.<br>What Zeiss told us was not wrong. But the magnitude of the problem was rather exagerated.

<p>Wow. Thanks, QG!</p>

The transport mechanism must be switched over

 

Hi Q.G

Is it possible to do this with Contax 220 back to shoot 120 film?

 

Thank you!

<p>Hi all...forgive if the question has already been asked.....a friend has just picked up a mint condition Contax 645...with 2 film backs. 1 is for 120 film..the other is for 220 film. Wanted to know if he can use 120 film in the 220 back...as he has loaded a roll but the camera refuses to function...and yes he has turn it on.<br>

Any thoughts would greatly be appreciated.</p>

<p>Regards</p>

<p>Artur</p>

Hi DEGREEFOTO,

Did your friend figured it out? Was he able to use 220 for 120 film?

Thank you!

I've used 120 in 220 Hasselblad backs, although I don't make a habit of it as there's some guesswork involved and you can end up losing a frame(the back will wind on more film than needed for each exposure).

 

With that said, I wonder how a vacuum back on a Contax would do with 120...

I've used 120 in 220 Hasselblad backs, although I don't make a habit of it as there's some guesswork involved and you can end up losing a frame(the back will wind on more film than needed for each exposure).

 

With that said, I wonder how a vacuum back on a Contax would do with 120...

 

Thank you for your reply! I'll definitely get a proper back but I'm going on the trip tomorrow and wanted to know if it's okay to use it for 10 days.

I think you may have a spacing problem between your frames on the film due to the fact that the film bulk and therefore the diameter of the 120 film roll on the take-up spool will be greater at any given point than that for 220 film due to the paper backing. Therefore you may have some overlapping frames or possibly a greater space between the frames.There is only one way to know. Try it and let us know. 220 back are going for a song these days compared to 120 backs.

Going back to the OP's question . . . You say "the camera refuses to function" . . . In what way? It is, I suppose, possible that the camera senses that the wrong film is in the back OR that it thinks there is no film in the back. It is also possible that this particular back has a pressure plate that is too tight to wind film with backing paper OR that the back or camera is damaged in some other way. There's really not a lot of information to go on here.

 

It's not true that no pressure plate adjustment is needed. It really depends on the camera. The same is true of the film spacing issue. Adding thickness is going to INCREASE the distance that the film is moved. This means that overlapping frames should not be a problem when using 120 film in a 220. I suppose that it is possible, but doubtful, that the film could run out before the last frame.

 

35mm film doesn't suffer this problem, in most cases, because the measurement of film movement is done by a gear turned in the sprocket holes.