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Mamiya RB 120/220 6x8 Motorized Back Question

Robert Szilvassy , Aug 01, 2013; 08:34 p.m.

I was wondering if anyone has loaded a Mamiya RB 120/220 Motorized Back 6x8 or 6x7 with 35mm film with successful results? The 6x8 Back I have functions perfectly with 120 film in manual or motorized, tested with a test dummy 120 film. When I load a 35mm dummy film 24 exposures with the plate on 120 or 220, the film will not stop on 1, in manual or with the motor, it just keeps advancing until the 35mm roll is finished. I can't seem to find the catch, latch or pin or whatever detects the 120 film is loaded & stops at #1. I know this can be done easily with a normal 220 Back although I really wanted the 6x8 format, not necessarily the motor.

Responses

Jim Momary , Aug 01, 2013; 09:34 p.m.

Robert -

The back can be used in a manual mode, wherein you advance the film by hand using the knob on the top.

So, either leave it 'off' or take out the AAs and work by hand.

The instruction manual has a description to this effect.

Jim M.

Robert Szilvassy , Aug 02, 2013; 06:07 a.m.

Jim, I did refer to the manual, yes, the Back does function perfectly in manual mode by advancing the film by hand with the knob on top with a 120 roll film, although it will not stop at #1 when loading 35mm film. I can't figure out why the back detects a 120 Film, but does not detect there is a 35mm film loaded.

Neil Grant , Aug 06, 2013; 08:05 a.m.

isn't the presence of film detected at the top edge of the film? I think there's a small cog that is rotated when in contact with the backing paper. 35mm film being narrower wouldn't come into contact with this.

Robert Szilvassy , Aug 06, 2013; 01:36 p.m.

You are correct Neil, that cog is the piece that operates the counter. I am slowly progressing since my last post by trial & error. Although if I tape this clog to the main roller the problem I encountered is that the 35mm cassette eventually moves & jams the main roller therefore prevents it from rotating & the clog to count to stop at one. I tried to distance the 35mm cassette from the roller with a spacer, but that only functions at intervals, I can get to #1 when the film is almost all through. I think I either have to look for a proven (probably earlier) RB 220 Back I can use or hack this back for permanent use with 35mm film only.

Jim Bogner , Aug 12, 2013; 09:54 p.m.

You've confused me. How are you loading 35mm film? The back is for 120 or 220 film.

Robert Szilvassy , Aug 13, 2013; 06:34 a.m.

Yes Jim, the Back is designed for 120 or 220 Film although many photographers have loaded 35mm in Mamiya RB Backs. The RB Pro or RB Pro S Back are the ones they use to load 35mm Film. I photograph Panoramic Format landscape with Bronica ETRSi & 35mm Panoramic (24mm x 54mm) W Backs, now I was attempting to reach a 24mm x 75mm Panoramic Format with the Mamiya RB 6x8 Back. I will have to settle for a 24mm x 69mm Panoramic Format with a RB Pro S 6x7 Back.

Ray Butler , Aug 14, 2013; 06:43 a.m.

Robert,

There is another way to get seriously wide 35mm panoramic formats in the RB67. I took 24mm x 83mm shots in a 6x9 back on my Mamiya Universal, with no issues. I described how I did it in this thread. These backs can also be mounted on the RB67 via a combination of P and M adapters.

If you have a Universal and an S-shaped film back, you already have an M adapter; and if you mount one of the older Polaroid backs on your RB67, you already have a P adapter.

I don't have an RB67 but I do happen to have a P adapter. The 76mm "clear width" of the P adapter will probably limit the image format to the same 76mm width as with a native RB67 6x8 back. You won't get the full 83mm of the 6x9 back. But this is still getting the full 6x8 image width onto 35mm film.

BTW, as 35mm film has no backing paper, to avoid the risk of film fogging I recommend that you not use one of the multi-format "Type K" Universal backs with the red windows that can be slid open. Use a fixed-format, windowless 6x9 back.

Robert Szilvassy , Aug 14, 2013; 07:44 a.m.

Ray, I just received another Mamiya 6x8 Motorized Back which is probably a little earlier Model (Pro-S) to replace the one I tried with previously, a SD Model. The Roller on the 35mm Film Cassette side where the counter is has a different Roller system, the Roller is also much thicker than the SD model therefore the 35mm Film thus far seems to travel normally, functions well stopping at #1. I haven't fully tested (photographed & developed as yet) although so far, so good. Great to know from the info you provided my options haven't run out, if this Back fails in the end results.

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