4x5 backs on an RB67 (for the RH50)

MCB18 · Mar 29, 2025

Yeah I know this is an odd question, but I was wondering if anyone ever made an adapter to use 4x5 backs on the RB67, with the space that not using the rotating adapter gives you.

And yes, before anyone says it, I am fully aware that the RB67 cannot cover 4x5 film, that’s not relevant in this case.

I am just trying to use an RH50 70mm back which has the same image area as a standard RB67 6x7 back.

ic-racer · Mar 29, 2025

Maybe the Horseman 6x9cm to 4x5" back could be modified to fit the RB.

Dan Fromm · Mar 29, 2025

MCB18 said:
Yeah I know this is an odd question, but I was wondering if anyone ever made an adapter to use 4x5 backs on the RB67, with the space that not using the rotating adapter gives you.

And yes, before anyone says it, I am fully aware that the RB67 cannot cover 4x5 film, that’s not relevant in this case.

I am just trying to use an RH50 70mm back which has the same image area as a standard RB67 6x7 back.

Um, er, ah, whatever adapter for the RH 50 you come up with will add extension. How will you focus?

See https://www.shoot70mm.com/cameras_backs.html, which discusses Mamiya's own 70mm roll holder for the RB67.

MCB18 · Mar 29, 2025

ic-racer said:
Maybe the Horseman 6x9cm to 4x5" back could be modified to fit the RB.

Heh, this would actually be perfect without modifications! Though thankfully for my wallet, it turns out to be unnecessary.

Dan Fromm said:
Um, er, ah, whatever adapter for the RH 50 you come up with will add extension. How will you focus?

Thankfully the RB67 has about 15mm of distance between the actual body attachment (not the graflock on the rotating adapter) and the film plane. And, conveniently, the Graflock “XL” plate is attached with 4 screws that I can mount the adapter I make to. I already modeled the RB67 attachment (will need to buy some screws from McMaster Carr for the attachment mechanism), just waiting on the back to get here to model the plate that attaches to that side. Graflock film plane is 5mm back from the face, 10mm should be absolutely fine for a simple adapter like this.

Dan Fromm said:
See https://www.shoot70mm.com/cameras_backs.html, which discusses Mamiya's own 70mm roll holder for the RB67.

And yes, I am well aware that the RB67 has its own 70mm back, but they are very expensive and require type 2 perfs, and the RH50 is… neither of those.

Monday317 · Mar 29, 2025

MCB18 said:
Yeah I know this is an odd question, but I was wondering if anyone ever made an adapter to use 4x5 backs on the RB67, with the space that not using the rotating adapter gives you.

And yes, before anyone says it, I am fully aware that the RB67 cannot cover 4x5 film, that’s not relevant in this case.

I am just trying to use an RH50 70mm back which has the same image area as a standard RB67 6x7 back.

Maybe there’s some sheet metal genius who could figure something out for you but adapting an RH50 back and successfully getting the film plane in the right distance for proper focusessing is unlikely. We should all just wait for Mamiya to follow in Pentax’s footsteps with the Model 17, and see if they won’t grace us with the RB69. Or maybe a rotating back to fit a Super 23 or Universal..?

Did I also mention peyote and LSD go great together?

MCB18 · Mar 29, 2025

Monday317 said:
Maybe there’s some sheet metal genius who could figure something out for you but adapting an RH50 back and successfully getting the film plane in the right distance for proper focusessing is unlikely.

I have 10mm to play with, so 3D printing is a viable option. I can also adjust the screws on the back by tiny amounts in order to get the focus exactly right, so I’m not super worried.

Monday317 · Mar 29, 2025

MCB18 said:
I have 10mm to play with, so 3D printing is a viable option. I can also adjust the screws on the back by tiny amounts in order to get the focus exactly right, so I’m not super worried.

Well then, if you can get the rotating adapter to cooperate mechanically, you may be in business with the modification. It’s beyond my expertise to suggest specifics, so !

reddesert · Mar 29, 2025

MCB18 is going to remove the rotating adapter. Without removing the rotating adapter, the film plane would be way too far back, and there also might not be room to fit a 4x5 holder. That's also why the 6x9 to 4x5 extension back that ic-racer posted would not help. One can extend the film plane backward on a view camera, but on an SLR it needs to end up in the right place. It will be good to plan on some means of adjustment using screws and/or shims.

Another question is whether the new "4x5 back" will interfere with any overhang on the back of the camera. The WLF will likely be ok, and the prism might be ok, since I think it has some height to clear the rotating backs.

I have a Mamiya Universal that somebody long ago milled out to allow fitting a 4x5 film holder. The camera doesn't actually cover 4x5, and my guess is perhaps they wanted to shoot 4x5 Polaroid. They didn't get the back spacing quite right, I think, and someday I'll adjust it. I got it when such things were in low demand, in part because even with being sort of an incomplete effort, it was a machining job I wouldn't be able to do myself.

ags2mikon · Mar 29, 2025

You may be able to use the Polaroid adapter plate that was used with the first version of Polaroid back for starters. Maybe?

aconbere · Mar 30, 2025

I haven’t tried it but you might also need to worry about the internal baffles. I know when using the 6x8 you need a special 6x8 rear baffle or you’ll get mechanical vignetting. Maybe you can just remove the whole thing.

The mamiya press P adapter is also promising since that allowed the polaroid film packs to be attached which is all getting close to the right measurements.

FriedLouisStudio · Mar 30, 2025

Just a little side note that might be of interest...

Back in my parents' studio we sometimes shot Tri-X sheet film with our RB-67 if we only needed a couple of shots. But it wasn't 4x5, it was 2-1/4 x 3-1/4 (6x9cm).

We were already using standard 2-1/4 x 3-1/4 film holders to shoot contact-printed ID photos (with a reduction back on a huge Agfa/Ansco studio camera). It turned out that these film holders fit EXACTLY on the RB-67's film back locking rails... with no light leak. (Of course, it wasn't intended that way, but it fit right in with my father's let's-experiment methods and motto - "An amateur knows how to follow the rules; a professional knows how to break them.") It worked!

A circa-1980 portrait of my sister my father shot this way: 2-1/4 x 3-1/4 TX sheet film in the RB-67, under our usual fluorescent lighting:

MCB18 · Mar 30, 2025

FriedLouisStudio said:
Just a little side note that might be of interest...

Back in my parents' studio we sometimes shot Tri-X sheet film with our RB-67 if we only needed a couple of shots. But it wasn't 4x5, it was 2-1/4 x 3-1/4 (6x9cm).

We were already using standard 2-1/4 x 3-1/4 film holders to shoot contact-printed ID photos (with a reduction back on a huge Agfa/Ansco studio camera). It turned out that these film holders fit EXACTLY on the RB-67's film back locking rails... with no light leak. (Of course, it wasn't intended that way, but it fit right in with my father's let's-experiment methods and motto - "An amateur knows how to follow the rules; a professional knows how to break them.") It worked!

A circa-1980 portrait of my sister my father shot this way: 2-1/4 x 3-1/4 TX sheet film in the RB-67, under our usual fluorescent lighting:

View attachment 395047

Yup! RB67 uses the standard grafloc 23 attachment system, so some 2x3 sheet holders will fit perfectly. I couldn’t find any of the grafloc kind so I just bought the special mamiya one, and honestly it’s quite nice and well worth the extra cost. I plan to shoot Instax film on it at some point, but I can also shoot normal film and plates as well

Alan Edward Klein · Mar 30, 2025

Can you adapt the Polaroid attachment for the RB67 to use regular film?

xkaes · Mar 30, 2025

Alan Edward Klein said:
Can you adapt the Polaroid attachment for the RB67 to use regular film?

Great idea.

Another point to consider is that the flange distance does not have to be exact because the RB has a bellows. As long as you get the film plane at infinity or slightly past infinity, the lens be be useful simply by adding a little extension. So micro-millimeter measurements are not needed.

MCB18 · Mar 30, 2025

Alan Edward Klein said:
Can you adapt the Polaroid attachment for the RB67 to use regular film?

Unfortunately no, not really. Not without substantial modifications anyway.

xkaes said:
Another point to consider is that the flange distance does not have to be exact because the RB has a bellows. As long as you get the film plane at infinity or slightly past infinity, the lens be be useful simply by adding a little extension. So micro-millimeter measurements are not needed.

The attachment mechanism also allows for slight adjustments, since it basically uses 4 bolts that “grab” the back in order to hook to the camera. I can turn them slightly to get those fine adjustments, thus allowing for normal use of the viewfinder.

Alan Edward Klein · Mar 30, 2025

Someone previously asked how you are going to focus the shot. The ground glass is set for the Mamiya-designed RB67 film plane. If you move it with the new adapted film holder, the focus plane on the ground glass will no longer match.

MCB18 · Mar 30, 2025

Alan Edward Klein said:
Someone previously asked how you are going to focus the shot. The ground glass is set for the Mamiya-designed RB67 film plane. If you move it with the new adapted film holder, the focus plane on the ground glass will no longer match.

Again, without the rotating back, I should be able to make an adapter with the same film plane as the rb67 normally has. I am currently making the model in fusion, I’ll post a picture of it in a bit.

Arthurwg · Mar 30, 2025

aconbere said:
I haven’t tried it but you might also need to worry about the internal baffles. I know when using the 6x8 you need a special 6x8 rear baffle or you’ll get mechanical vignetting.

Not sure that's true for the RB67 Pro SD.

Donald Qualls · Mar 31, 2025

FriedLouisStudio said:
2-1/4 x 3-1/4 TX sheet film in the RB-67,

I have a couple 2x3 Grafmatics -- they give more options on how to use my RB67, since they fit perfectly. Yes, vignetting will be a thing, but it's also a thing with a 2x3 mount Graflex 23 roll film back, and I've used that as well. Not to mention Graflex 22 and RH10/RH20.

I do agree, however, it ought to be possible to adapt a 4x5 film back the same way folks have adapted Instax backs to the RB -- by deleting the rotating mount. That would get something close to an 8x8 image on the 4x5 film (but 4x5 in some stocks is cheaper than the four emulsions of 2 1/4 x 3 1/4 that are readily available, and equipment for handling/processing 4x5 is easier to come by).

paul ron · Wednesday at 7:40 AM

ive never seen one but here is a video of someone using a sheet film adapter.

MCB18 · Wednesday at 7:50 AM

paul ron said:
ive never seen one but here is a video of someone using a sheet film adapter.

The “J” version is actually really common, it’s the “A” version that is more rare. I have one, I got it to shoot Instax film with the RB. Processing involves running the film through a separate processor, so not as nice as an integrated back. But in total the holder and instax printer cost me like… $60? As opposed to $300+ for a dedicated back

Nokton48 · Wednesday at 10:18 AM

SK Grimes Hasselblad Compendium Adapter 180mm Sonnar by Nokton48, on Flickr

SK Grimes made a limited run of this 4x5 Graphic Adapter, they made up six units for our Plaubel Makiflex Community. I use this frequently with Graflex RH50 70mm Backs. Some parts were 3D printed, other parts made up on their CNC's.

I would think they could make one up for RB67??

MCB18 · Wednesday at 10:54 AM

The back is supposed to be delivered Friday so hopefully I’ll be able to get the last few measurements I need for the back. After that I just need to figure out how to get the part 3D printed, as I don’t have a printer… I feel confident enough about this design that I can probably just get it printed once, but there’s always the possibility that I run into issues. I also need to find some light seal foam for it… the adapter has a small groove that foam must be added to.

abruzzi · Wednesday at 11:25 AM

MCB18 said:
The back is supposed to be delivered Friday so hopefully I’ll be able to get the last few measurements I need for the back. After that I just need to figure out how to get the part 3D printed, as I don’t have a printer… I feel confident enough about this design that I can probably just get it printed once, but there’s always the possibility that I run into issues. I also need to find some light seal foam for it… the adapter has a small groove that foam must be added to.

If you have a model already built there are a lot of services online that printing for you at reasonable cost. In the past I've used https://treatstock.com and have been happy. They don't print themselves, but function as a front to match people who need prints with people who can do the printing.

For some of the work I was doing, it was cheap enough to print frequently to test changes to the design.

paul ron · Wednesday at 12:55 PM

with 3d technology its a very good chance to get one custom made. you would be surprised there are so many people doing this in their home and willing to collaborate with you just for the fun of it. ask around? it could be a group project and making a few is easy once you get the STL files worked out.

as for light seal foam... microtools.com was a great source. we also had mr goodman but im not sure he is doing seals anymore.

if you do 3d print it, i hope you'll post the STL files?

4x5 backs on an RB67 (for the RH50)

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