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05-11-2010, 05:19 AM   #1
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Pentax 645N - 120 film in 220 magazine ?

Hi,

I was just told that it should be possible to use 120 film in 220 magazine with the Pentax 645N. Could anybody around confirm this? thanks.

05-11-2010, 11:21 AM   #2
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QuoteOriginally posted by Matus Quote
Hi,

I was just told that it should be possible to use 120 film in 220 magazine with the Pentax 645N. Could anybody around confirm this? thanks.
People swear both ways on this. Some say it can cause major damage, others say its great with no problems... Still othere say a small modification to the 220 back is necessary. A quick Google search brings up a lot of information, but I haven't been brave enough to try it

120 film with 220 back? - Photo.net Medium Format Forum
220 film back - compatible with 120 film - Photo.net Medium Format Forum

From the Flickr 645 group:
Flickr: Discussing 120 film, 220 back in Pentax 645,645N,645N? and 645D

Let me know if you decide to try it and if it works

Last edited by mikebob; 05-11-2010 at 11:22 AM. Reason: spelling!
05-11-2010, 12:53 PM   #3
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I have sort of tried it. I took the backing paper from a used 120 film, wound it back on a spool the same way it would be wound around unexposed film, and shot this without a lens, drawing squares where the frames ended up.

This isn't exact, since film thickness would move the frames a little, but my conclusion was as I recall that it would work fine and might let me fit an extra frame on the roll (depending on my choice of film). There is one and a half problem though:

The camera doesn't know when you're out of film, so you have to track that yourself, and you have to shoot a number of extra pictures before opening the camera to get the traling paper wound up.

I probably tested this in a 645 (not N), but that shouldn't matter.
05-11-2010, 01:40 PM   #4
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If you think about it, the film gate - register distance - is determined by the camera, the back just holds the film to it. There's a piece you unscrew and screw back the other way - that tells the camera when the film's out. However, it doesn't, not fully. But it does work.

That said, I did the mod to a 220 back, and yes, it works. There's a thread on it here somewhere... can't find it, so maybe not. My results? I wouldn't do it as a habit, I'm not sure - all theory to the contrary - that the results were as sharp as with the 120 back.

05-11-2010, 02:25 PM   #5
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Original Poster
- mikebob -

I am and experimental physicist - I had to try .... and ... it works !!!

In the second link you have provided is a detailed description, but let me put my version here (I checked it twice!):

So - when one takes out the back and looks between the latches that can be flipped out to load/remove the film spools - there is a little black plastic rectangular of size about 12 x 4 mm. On one of the long sides it has a small teeth. This little "thing" is attached by two small screws. One of these screws is slightly obscured by the steel teeth that holds the film insert attached to the camera. When I have bought the camera with the 220 magazine, the teeth was pointing towards the back of the camera (away from film plane) and was easy to overlook.

So - to find out how this should work I used 2 films to figure out (one would have been enough though)

1) with the "thing" in its original position (teeth pointing away from the film plane) I loaded one 120 film in the back and shot 20 exposures until the film went completely through the camera. Then the camera did a short winding attempt and showed "E" on the display, which I guess stands for Error.

2) Unscrewing the 2 small screws I turned the plastic "thing" such that the teeth was pointing towards the film plane. Loaded another film and shot exactly 16 frames. After that the camera wounds the rest of the film onto the reel and showed "End" on the display.

So - it seems that with the teeth pointing towards the film the camera (or towards the shutter when the magazine is mounted on the camera) expects 120 film. What remains to be checked is simply to shoot a film or two in this settings and see that everything is OK. I would guess everything will be fine

I do not expect a problem with the film pressure plate is this has a lot of space to move (much more than the one in my Roilleiflex T)

... now all of you will run to get those cheap 220 inserts ...
05-12-2010, 09:52 AM   #6
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QuoteOriginally posted by Matus Quote
- mikebob -

I am and experimental physicist - I had to try .... and ... it works !!!

...
Excellent news Matus. I'll have to try it

In one of the links I forwarded, somebody mentioned that a Pentax service technician stated that the plastic "tooth" was the only difference between the backs. Maybe Eric over at http://www.pentaxs.com/ would know for sure. I'll send the question to him.
05-12-2010, 11:32 AM   #7
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Oh I know I'd posted a sample
https://www.pentaxforums.com/forums/pentax-medium-format-645-6x7-645d/87027-p...tml#post913903
05-13-2010, 08:02 AM   #8
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QuoteOriginally posted by Nesster Quote
Hmmm... well, that's not a good result (the picture is great, by the way). Maybe it's not possible then without risking the last couple of exposures.

05-13-2010, 08:51 AM   #9
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To be honest, after comparing again to the 120 back, the 220 doesn't leave much more backing out, and it really is safe to use.

Plus, other samples of the 645 or later models may behave slightly differently.

Last edited by Nesster; 05-13-2010 at 09:41 AM.
05-13-2010, 09:42 PM   #10
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I have 2 120 and 3 220 backs, so converting the 220's into 120's is helpful. The risk seems minimal, but in any case, shooting a test film can eliminate it. No oner seems to have reported back that it has a detrimental effect on the IQ.

Yet, I still will offload at least one back, I really will not be carrying so many around! One spare for each film type should do.
05-14-2010, 09:11 AM   #11
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The response back from Eric over at www.pentaxs.com was:

QuoteQuote:
The back determines the film metering whether it pushes on the 120/220 gear or doesn't push on it.
So, the back decides if it will be 120 or 220 I replied with:
QuoteQuote:
True, and the part that does that is a simple piece of plastic with 1 screw in it – notched for 120 and not notched for 220 and identical in every way on both backs. So, the theory is that reversing that plastic piece is all that is required to change a 220 back to a 120 and vice versa. Everything else seems identical, including the pressure plate pressure. Would you say this is a valid statement?

Thanks so much for answering me. I appreciate it! Many of us have extra 220 backs that are increasingly useless and it would be great to be able to use them for 120. Of course this may drive up the cost of 220 backs to the same as 120, hence people’s lack of definitive answers on this.
No answer yet. Hopefully I haven't worn out my welcome with him!

Mike

Last edited by mikebob; 05-14-2010 at 12:01 PM.
05-19-2011, 03:15 PM   #12
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Well things if anything are getting worse. 120 inserts are costing a fortune whereas 220 inserts are about half the price or less. However we don't seem to have reached a definite conclusion. MiIkeBob was waiting for a definite answer from a Pentax expert but there the trails runs out.

So can anyone here say that the conversion is possible because he has done it successfully and is now using a 220 magazine for 120 film faultlessly?

Spending even half what it costs to buy a 120 insert to get a 220 which has faults or doesn't work properly is still a waste of money.

Thanks

asahijock
05-19-2011, 03:31 PM   #13
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I have not seen any detrimental effect myself, and am using two 120s and two 220s without discriminating between them.
05-24-2011, 10:42 PM   #14
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I'm in Pentax's Professional Service program and I asked the rep about the claim that the backs can be converted. The answer is:
NO.

This should put an end to the discussion and speculation on this topic.
05-26-2011, 08:05 AM - 1 Like   #15
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If you provide no reasoning whatsoever, it will never put an end to the discussion.
Just referring to an unnamed rep does not tell me anything.
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