P645 Insert - Difference between 120 and 220

pentaxuser · May 28, 2018

Without wishing to appear rude, can I say that this thread is really addressed only to those who have converted a 220 P645 insert to 120 in respect of answers. Anyone contemplating conversion of a 220 to 120 might of course be interested.

On the PentaxForums site, there has been a long-standing thread on this matter. What is clear is that you can make a 220 work as a 120 and given the difference in price between the two and what appears to be the relative scarcity of the 120 v 220 which is reflected in price it would appear on the surface, to be a "no brainer" to make the conversion.

However in the last couple of weeks a member on the MF section of Pentaxforums has pointed out and shown, with pictures of the inserts, that the pressure plate is different. To allow for there being two layers( backing paper and film) the 120 pressure plate is flat whereas the 220 has a raised lip as there is only one layer( the film) for most of the roll.

He quotes someone called Eric whom I assume to be an expert P645 repairman who has advised against the conversion because the lip on the 220 will apply extra strain on the camera's motor when it tries to pull through a two layer 120 film with possible motor problems. Clearly motor problems will not arise on the first few 120 films but eventually he appears to predict that motor issues in the long term will be inevitable.

The thread's age ( about 7 years) and this knowledge that the conversion works, has now been known for at least that amount of time and I have asked for responses from P645 "converters" on their experience of otherwise of motor problems but nothing back so far. However the PentaxForums are much less used than Photrio and there are known P645 users here.

So, can any user who has done the conversion let me know of how long ago he/she did the conversion and/or how many rolls he/she has put through since.

I'd be particularly interested in GRHazelton's experience, whom I recall, was one such known converter

Thanks

pentaxuser

paul ron · May 28, 2018

is this the thread?

https://www.pentaxforums.com/forums...1062-pentax-645n-120-film-220-magazine-2.html

pentaxuser · May 28, 2018

That's the one, Paul. I fear that we will only find one or two "converters" here but It sounded as if GRHazelton for one, who visits here, converted way back in 2011. If he and hopefully others converted back then and have run quite a lot of rolls through the converted 220 insert without issues then we have a basis for feeling fairly confident that the potential motor problems are a long way down the road.

pentaxuser

abruzzi · May 28, 2018

I can’t speak to the reliability of such a conversion, I was considering a Pentax 645NII a few months back when I decided on a Pentax 67 instead. However I can tell you that when “Eric” is mentioned, it is usually referring to Eric Hendrickson, a former Honeywell and later Asahi camera repairman in the US. He now runs his own repair shop here:

http://pentaxs.com/

pentaxuser · May 28, 2018

Thanks,abruzzi, for the info and link. If all else fails I may ask him how many repairs he has had to do on converted 220 inserts due to motor strain that he can attribute to the conversion

pentaxuser

Ian Grant · May 28, 2018

I've used a 220 insert for years with ot realising No issues, the pressure pale worked perfectly but if I'd not been checking the film counter I may well have had issues.. I never gave it a thought at the time.

Ian

Billy Axeman · May 28, 2018

I have run only one 120 roll in a converted 220 magazine in a Pentax 645N as a test and it neatly counts to 16 and I can see nothing wrong with the negatives.

However, there is definitively a difference in thickness of the pressure plate. The 220 magazine has a pressure plate with edges that are reduced in thickness (1.25 mm) compared to the 120 (1.45 mm), measured with a caliper.

The difference can be seen in the photo from post #28 in the thread indicated by paul ron (post #2). So, I would say Pentax has machined the pressure plate for some reason and I decided to use the magazines as intended.

pentaxuser · May 28, 2018

Billy Axeman, thanks for the measurements. I have just had a thought - almost a revelation really. With a difference of as little as 0.2 of a millimetre it makes me wonder what it is about the "mechanicals" of the insert that would cause a problem. If the only difference between the two inserts is the pressure plate thickness then I can understand why the batteries that power the "cogs" pulling the film through have to work harder but unless the actual "mechanicals" are different and no-one seem to be suggesting they are, then surely the only issue will be that the batteries have to work harder with a 220 conversion and thus need replacing more frequently

Why would this wear out anything mechanical? The only explanation I can now think of, is that the batteries are in fact so powerful that they overcome the extra pressure of the 220 plate but in so doing can strip the cogs teeth or wear them down to an extent that they cease to work.

I would have thought that the power of the batteries would fail to be able to wear out the teeth on the cogs and we already know that Ian Grant has not experienced a problem . Can anyone think of another reason why damage is possible?

pentaxuser

GRHazelton · May 28, 2018

As one who was cited in this thread - perhaps my only chance for fame! - I must admit that I've not had extensive experience in the conversion. So far my 645n shows no signs of problems due to my "abuse." I hope that other "abusers" will collaborate my experiences.

destroya · May 28, 2018

i have used my converted 220 to 120 cartridges for many years and have so far had no ill effects, as have many others I know. is it bad for the motor? hard to tell. I hope to never find out

Sirius Glass · May 28, 2018

I do not have knowledge about Pentax, however with Hasselblad to Hasselblad repairman can make the conversion. See what can be done by Pentax repair men.

MattKing · May 28, 2018

FWIW, when Mamiya used to maintain their own film camera forum, it included advice from Mamiya USA that 120 film could be used in 220 inserts, but the extra thickness of the film would contribute to premature wear of the springs in the inserts.
IIRC, this was in reference to the 645 inserts.

Billy Axeman · May 29, 2018

pentaxuser said:
Billy Axeman, thanks for the measurements. I have just had a thought - almost a revelation really. With a difference of as little as 0.2 of a millimetre it makes me wonder what it is about the "mechanicals" of the insert that would cause a problem. If the only difference between the two inserts is the pressure plate thickness then I can understand why the batteries that power the "cogs" pulling the film through have to work harder but unless the actual "mechanicals" are different and no-one seem to be suggesting they are, then surely the only issue will be that the batteries have to work harder with a 220 conversion and thus need replacing more frequently

Why would this wear out anything mechanical? The only explanation I can now think of, is that the batteries are in fact so powerful that they overcome the extra pressure of the 220 plate but in so doing can strip the cogs teeth or wear them down to an extent that they cease to work.

I would have thought that the power of the batteries would fail to be able to wear out the teeth on the cogs and we already know that Ian Grant has not experienced a problem . Can anyone think of another reason why damage is possible?

pentaxuser

If you take a look into the back of the camera (without magazine) you can see two blank pairs of guide rails left and right. I have measured the distance between them, and also the width of the pressure plate and it looks the pressure plate is resting on the outer two guides (the thin ones) and the film is guided over the inner two guides. So if the pressure plate is made thinner on the outside the middle part of the plate comes closer to the inner two guides leaving less space for the film.

That's all I can say. There is no way to tell how the tolerances are for the space left over for the film to move along the inner guides. But knowing the habit of Pentax to over design the details I wouldn't be surprised if these tolerances are quite narrow.

Now, following your line of thought I would say 'if' the pressure plate in the 220 modified magazine causes more resistance of the 120 film on the inner two guide rails (because it is thicker with the backing paper) the motor transporting the film must deliver more power, and it will draw more current from the battery. So this motor is wearing out faster because it is loaded more and its temperature will rise too. Also, the forces on the gears in the drive train between motor and magazine are higher than normal and they are wearing out faster.

The bottom line is that these mechanics are quite subtle and we don't exactly understand the details, so I would say it's better to take no risks and pay a few dollars more for the 120 magazine. Also, any repairman will ask more for a modification than the difference between a 120 and a 220 magazine (plus shipping costs).

Edit 29/05/18 - 3-rd paragraph changed.

Billy Axeman · May 29, 2018

I also measured the backing paper (HP5+) and it is about 0.1 mm. I remeasured the edges of the pressure plates on several places and the 220 plate is actually closer to 1.30 mm (I said 1.25 in post #7). So the edge of the plate in the 220 magazine is 1.30 mm and in the 120 magazine 1.45 mm, with a difference of 0.15 mm coming close to the backing paper. This is all on the limits of the resolution of my caliper. FWIW.

pentaxuser · May 29, 2018

GRHazelton said:
As one who was cited in this thread - perhaps my only chance for fame! - I must admit that I've not had extensive experience in the conversion. So far my 645n shows no signs of problems due to my "abuse." I hope that other "abusers" will collaborate my experiences.

Thanks for the reply GR. There's famous and there's valuable. I'll settle for the later any day and you are certainly the latter the latter. Any idea of how many rolls you might have put through since the conversion?

Thanks

pentaxuser

pentaxuser · May 29, 2018

Thanks all for the very informative replies. It might be worth saying that the conversion is relatively simple and can be done by the user for nothing instead of paying the charge of a Pentax repairman who, at least in Eric's( well known Pentax repairman) case, would advise against it due to presumably the kind of difficulties that Billy Axeman has mentioned as possible in his post.

pentaxuser

johnha · May 29, 2018

I've followed the thread recently on Pentaxforums, I don't have a P645 (but have a Mamiya 645 which has been the subject of similar queries). My take on this, having looked at eBay prices, is that unless you already have a stash of 220 inserts, it's not worth the risk (I wouldn't risk it if it was my camera). 220 film was always less popular than 120, why there would be more 220 inserts available than 120 seems strange. I've just searched and found no significant price advantage of 220 over 120 inserts (OK maybe a difference of $20 but you'd want to risk a camera for that?).

John Koehrer · May 29, 2018

Seems like there's quite a few could be's & maybes floating around this one.
The stop function isn't influenced by film/paper thickness. it's mechanical and only mechanical. The drag
will be slightly heavier with 120 from that .015mm in thickness ain't squat. It's also only pulling half the
length of film vs 220.
So maybe you won't hurt nothin'

BTW the abundance of 220 inserts available may have a bit to do with the lack of 220 film.Maybe? Could be?

Billy Axeman · May 30, 2018

When you are buying a magazine (insert) be sure it comes with the holder. It prevents scratching the transport rolls and the pressure plate during transport. It also has a rubber seal in the edge to keep dust out and it makes the unit light tight. In this way you can take several preloaded magazines with you for a quick swap.

pentaxuser · May 30, 2018

Billy Axeman said:
When you are buying a magazine (insert) be sure it comes with the holder. It prevents scratching the transport rolls and the pressure plate during transport. It also has a rubber seal in the edge to keep dust out and it makes the unit light tight. In this way you can take several preloaded magazines with you for a quick swap.

Your post raises an interesting question for me to which I do not know the answer. If you have the holder and a changing bag then presumably you can release the insert and safely replace the holder so the exposed film is light tight. You can then insert a fresh film. So far so good, I think.
Is there any way you can then replace the original film taken out on say frame 8 and set the camera up again so that it continues to shoot from frame 8 or does the camera "think" that a new insert means a fresh film and proceeds to wind it on to frame 1 so you lose a few frames automatically and there is no way of overriding the camera's action? If so , any idea how many frames are lost? It were possible to do something like this then armed with a changing bag and in exchange for a bit of effort you have a form of interchangeable backs?

pentaxuser

Billy Axeman · May 30, 2018

pentaxuser said:
Your post raises an interesting question for me to which I do not know the answer. If you have the holder and a changing bag then presumably you can release the insert and safely replace the holder so the exposed film is light tight. You can then insert a fresh film. So far so good, I think.
Is there any way you can then replace the original film taken out on say frame 8 and set the camera up again so that it continues to shoot from frame 8 or does the camera "think" that a new insert means a fresh film and proceeds to wind it on to frame 1 so you lose a few frames automatically and there is no way of overriding the camera's action? If so , any idea how many frames are lost? It were possible to do something like this then armed with a changing bag and in exchange for a bit of effort you have a form of interchangeable backs?

pentaxuser

I don't think it's possible to swap a film-holder halfway.

The Pentax 645N manual has a chapter 'Unloading the film mid-roll' (page 22) but it uses the little button below the film-holder to forward wind the film completely before removing it. That's it, they say nothing about re-inserting a film-holder. The magazine has also no means to send info to the camera for a frame number, for example with contacts.

Edit 30/05/18 - The Pentax 645 (without N) works differently, it has some sort of manual film wind knob which can be used when the battery runs out. But also here I think it's not possible to re-insert a film-holder with the film halfway.

trendland · May 30, 2018

johnha said:
I've followed the thread recently on Pentaxforums, I don't have a P645 (but have a Mamiya 645 which has been the subject of similar queries). My take on this, having looked at eBay prices, is that unless you already have a stash of 220 inserts, it's not worth the risk (I wouldn't risk it if it was my camera). 220 film was always less popular than 120, why there would be more 220 inserts available than 120 seems strange. I've just searched and found no significant price advantage of 220 over 120 inserts (OK maybe a difference of $20 but you'd want to risk a camera for that?).

I indeed noticed it different and found the special reason. The price difference was given for new equipment : If I remember correct you'd to pay more than 180 bucks in addition for the 220 insert. Many wonder about but 1) Pentax allways wanted to make lot of money with special extra equipment and a 220 insert was such kind of "extra" equipment. 2) the much more number in sale was of course the 120 insert. So the number of manufacturing was much smaler with the 220. (No need to sell it such expensive from my point because of 98,7% same parts........)
Today it has changed (90% of "Pentaxusers" changed to digital)
I indeed remember the time it began : 2008 - most were selling their medium format cameras for less (Pentax then discontinued the 4,5 x 6 / 6 x 7 series)
AND THE MARVELOUS OPTION OF THIS PEOPLE ????? SHORT ANSWER : They invested money in 12Mp APS C stuff - what a pity.
But from that reason the pricing of used equipment comes down to the max.
And today the remaining shooters might have not the strong need to 220 inserts caused from the lack of 220 films therefore the difference (220 more cheap in comparison to 120 with used equipment)
But if you compare (from Pentax price list 2008) the 120 insert with the "used" pricing today you might get 3 magazines in extreme good condition for the same price - do we might say : " It is real cheap today? "
At last you might be right : There should be no need to "come to" 220 inserts with 120 Films.

with regards

PS : The opposite makes real sence from my point = 220 inserts with 220 films -
never try 120 inserts to 220 films

trendland · May 30, 2018

pentaxuser said:
Without wishing to appear rude, can I say that this thread is really addressed only to those who have converted a 220 P645 insert to 120 in respect of answers. Anyone contemplating conversion of a 220 to 120 might of course be interested.

On the PentaxForums site, there has been a long-standing thread on this matter. What is clear is that you can make a 220 work as a 120 and given the difference in price between the two and what appears to be the relative scarcity of the 120 v 220 which is reflected in price it would appear on the surface, to be a "no brainer" to make the conversion.

However in the last couple of weeks a member on the MF section of Pentaxforums has pointed out and shown, with pictures of the inserts, that the pressure plate is different. To allow for there being two layers( backing paper and film) the 120 pressure plate is flat whereas the 220 has a raised lip as there is only one layer( the film) for most of the roll.

He quotes someone called Eric whom I assume to be an expert P645 repairman who has advised against the conversion because the lip on the 220 will apply extra strain on the camera's motor when it tries to pull through a two layer 120 film with possible motor problems. Clearly motor problems will not arise on the first few 120 films but eventually he appears to predict that motor issues in the long term will be inevitable.

The thread's age ( about 7 years) and this knowledge that the conversion works, has now been known for at least that amount of time and I have asked for responses from P645 "converters" on their experience of otherwise of motor problems but nothing back so far. However the PentaxForums are much less used than Photrio and there are known P645 users here.

So, can any user who has done the conversion let me know of how long ago he/she did the conversion and/or how many rolls he/she has put through since.

I'd be particularly interested in GRHazelton's experience, whom I recall, was one such known converter

Thanks

pentaxuser

If you use the 220 insert with 120 films you might have not an extreme risc to broke your camera. Because this proffessional stuff is designed to handle more than 2000 films without problems - I can't say exactly but we may speculate if 20.000,- films is the more correct number.
So the risc of a mechanical problem isn't that case - no fear !

with regards

Billy Axeman · May 30, 2018

Yes, why would you listen to the advise from an experienced man like Eric Hendrickson, who has repaired all existing Pentax camera's in the world his whole life long, earning E 30,- from the difference between a 120 and 220 insert, and then wearing out a E 500,- camera in excellent condition.

trendland · May 30, 2018

Ok - that is a quite good argumentation to sent him 220 inserts for adjustments (to use it as 120 insert) But from financial view - does it realy make sense
(accept to Eric H - who possible like that money) ?

with regards

PS : Are there realy broken 645N out there (with motor problems) from using 220 inserts with 120 film ?

P645 Insert - Difference between 120 and 220

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