Mamiya RB67 Pano conversion?

[removed-user-1]

I'm not sure if this belongs in the medium format forum or the pano forum.

Anyway, I have an idea and I was wondering if anybody else has tried it. I want to modify a standard RB67 dark slide to cover only half the frame, so that I can take 28mm x 70mm (roughly) panos on 120 film. This would produce two pano shots per 6x7cm frame without making the back a full-time pano back. Of course I would do this to an extra dark slide so I could still remove the back!

 

[Mike1234]

It should work just fine but you'll not be able to correct for the effective shift up for one image and shift down for the other. And don't forget that the darkslide needs to be in the reverse position of how you see it in the prism.

 

[Jeff Searust]

But you're just deleting half the frame-- this is not a panoramic shot. -- A panoramic shot involves a larger field of view and not just a thin picture.

 

[Mike1234]

There are many pano shooters who use normal and long lenses. But yes, these are really just thin images. It's the look of the format (thinner) that matters, IMHO.

 

[mrladewig]

But you're just deleting half the frame-- this is not a panoramic shot. -- A panoramic shot involves a larger field of view and not just a thin picture.

6X12 is just half a sheet of 4X5 film. 24X70 sounds about like the xpan format. Whats the difference?

The cut darkslide should work. It works fine for large format and many people do this. The disadvantage of that method versus a dedicated pano format is the pano is taken off the center of the lens.

 

[keithwms]

Sure, it'll work. You could make yourself a half dark slide and just invert that and take two shots per frame, side by side. This is what some LF 8x10 shooters do to get 4x10. With the rb 6x8 back you'd get two ~26x76mm images per frame.

Ultimately, though, you'll get no more neg size and actual resolution than you'd get from an xpan.... or a mamiya 6/6MF/7/7ii with a pano adapter. So then it begs the question, why so much gear for such a "small" frame! Still may be worth doing though.

Note that you can also run 35mm film through the rb. It is very easy to do, as I showed in various other threads. You can get the sprocket holes too if you like.

Another thing you could do, if you are willing to stitch electronically, is just take two shots... if you want to be fancy you can use a shift lens for that or the tilt/shift adapter with a short barrel lens. That'd give you an effective image dimension of, I don't know, 6x10 or something like that.

Another outlandish thing I have done is put a kaidan 360 lens on an rb to record a 360-degree image. You don't resolve any more than you would with 35mm or so, but it's all in one frame which is convenient.

 

[Lightproof]

A nice idea!
It leads to the question, if and where exactly the presence of the darkslide is supervised and how this interlock could be tricked.

The modification for the GX680 would be the removal of one limit switch in the film holder - or the addition of an external bypass switch.
You could compensate for the shift, too. I guess I have to try that...

 

[keithwms]

The darkslide interlock on the rb is easy to defeat.

But if it were me I'd just shoot to 35mm using the 6x7 or 6x8 back. All you do is cut a 120 spool in half, cut off a bit more, whittle a bit, poke the ends of the resulting thingymabobs into the 35mm canister, and take up the 35mm film on a normal 120 spool. Very easy.

 

[Sirius Glass]

Keith,

Can I assume that removing the film is done in the dark room?

Steve

 

[keithwms]

Yep! Or film changing bag....

One other thing to watch out for, when the 35mm roll reaches its end, it will resist winding. If you have a motor-driven winder, the motor may not tolerate this resistance... The film will not break, but the winder might well. So... better to do this with a hand winding mechanism if possible. At the end of a roll, my mamiya 645 afd motor-winder went aaaaaaaaaa! and had to be shut off manually to keep damage from being done to the winder motor. I also (stupidly) did this trick in a mamiya 6, which has a notoriously weak winder mechanism, and did a bit of damage to the winder registry. But it's okay now.

 

[k_jupiter]

Yep! Or film changing bag....

One other thing to watch out for, when the 35mm roll reaches its end, it will resist winding. If you have a motor-driven winder, the motor may not tolerate this resistance... The film will not break, but the winder might well. So... better to do this with a hand winding mechanism if possible. At the end of a roll, my mamiya 645 afd motor-winder went aaaaaaaaaa! and had to be shut off manually to keep damage from being done to the winder motor. I also (stupidly) did this trick in a mamiya 6, which has a notoriously weak winder mechanism, and did a bit of damage to the winder registry. But it's okay now.

Of course the solution is you take two 120 spools and wind tape on them to provide a 135 area for both supply and take up reels. You then load these off a bulk loading 50 or 100 foot film roll.
The purists might not approve, but shooting with the 50mm lens gioves you a great 35x70mm photo plus sprocket holes if you want.


tim in san jose

 

[Jeff Searust]

Why bother doing all this?

If you are just wanting a thin part of a 6x7 negative, just shoot it and crop it.

The other idea may be to get a 6x4.5 film back for your RB67 and shoot it horizontal.

 

[removed-user-1]

Why bother doing all this?

Just for fun.

Thanks for the suggestions everyone!

 

[k_jupiter]

Why bother doing all this?

If you are just wanting a thin part of a 6x7 negative, just shoot it and crop it.

The other idea may be to get a 6x4.5 film back for your RB67 and shoot it horizontal.

What a silly question! *L*

60x45mm doesn't look the same as 35x70 (actually about 35x67)

tim in san jose

 

[keithwms]

Why bother doing all this?

Why bother doing anything the normal way? Isn't that tedious?

 

[jasonhall]

I have done this with 35mm film in my RB67. I Made a mask that just popped in to the film back. It does not effect the dark slide and I place foam on it to hold the film flat to the pressure plate. I also made a take up spool to keep the film in line with the mask. Then I made spacers with a spare 120 spool to will hold the film canister in the correct position. With photoshop I made a mask for the view finder. The kit worked very well, I do need to make it again and refine my methods.

As I recall, I get 17 frames on a 36 exposure roll of 135. This does however require a 220 back to be used. Maybe the 120 back will work with a 24 exposure roll.

 

[k_jupiter]

I have done this with 35mm film in my RB67. I Made a mask that just popped in to the film back. It does not effect the dark slide and I place foam on it to hold the film flat to the pressure plate. I also made a take up spool to keep the film in line with the mask. Then I made spacers with a spare 120 spool to will hold the film canister in the correct position. With photoshop I made a mask for the view finder. The kit worked very well, I do need to make it again and refine my methods.

As I recall, I get 17 frames on a 36 exposure roll of 135. This does however require a 220 back to be used. Maybe the 120 back will work with a 24 exposure roll.

It should seeing as a 135 negative is 24x35 mm (without perforation holes). A 120 will give you 10 6x7 images on a roll or 11 or 12 135 images on a roll of 24.

tim in san jose

 

[jasonhall]

It should seeing as a 135 negative is 24x35 mm (without perforation holes). A 120 will give you 10 6x7 images on a roll or 11 or 12 135 images on a roll of 24.

tim in san jose

Well I guess either way, the 120 back will only allow you to get 10 shots no matter what size roll you use. Of course there is a way around useing a 120 back with a 36 exp roll. When you hit frame 10, just place the back in the dark(under your jacket or where ever) and pop it open enough to reset the counter. You just will not be able to use the wind stop to perfectly space your frame for the next several exposures. I do that anyway at the begining on the roll to squeeze out two or three more frames.

Jason

 

[removed-user-1]

Ok, I finally got around to cutting a slice out of an RB67 dark slide. The results are currently drying. In tribute to John Scarlata's 7x17" work, most of which was shot on Kodak TXP 320 and scanned (and stitched!) by yours truly, I used one of my remaining rolls of 120 size TXP for this.

I have to be careful, there are a couple gotchas waiting in the wings. First, as noted above, I have to remember that the lens inverts the image. So, when I shoot, I always use the top half of the film first, and say a sort of mantra: "compose for the top half, put the dark slide in the top half, expose the bottom half." For the second shot, it's reversed. Also, if the dark slide is even a little out of line, I'll get a trapezoidal frame... not exactly the look I'm after. Then there is the possibility of removing the back with the cutout dark slide in; therefore I don't push it all the way in, and anyway it has to be out a bit for the shutter to fire.

It works very well! I get two ~26x68mm images for each 6x7cm frame, and I can always shoot a full 6x7cm frame at any time on the same roll. Certainly a lot less gear to carry than a second dedicated pano camera (also cheaper at $3 for the extra dark slide).

The 65mm is not quite wide enough. That's ok, now I have another reason to save for the 50mm C lens.

 

[MiddleGrayStudios]

I'm with Jeff here. Why go through the process of trying to make a pano using a 6x7 back when you could just as easily crop afterwards, which would give you creative freedom for composition. Keep in mind if you were to try to do the process you speak of, you would also have to have precise marks on your focusing screen that equal that of your modified dark slide. If I were you, I'd just go with the using the 35mm film in the back and then cropping the sprocket holes out from the top and bottom for final output - it would also be much wider of an image. It is a pretty common alternative method of working and you can find plenty of videos that teach you how to do it via YouTube/Vimeo.

 

[removed-user-1]

I'm with Jeff here. Why go through the process of trying to make a pano using a 6x7 back when you could just as easily crop afterwards, which would give you creative freedom for composition.

I wrote about three different, and very detailed, responses to your post before I settled on this:

Why? Because I can, that's why.