All the panoramic stuff I see here makes this seem pretty mundane, but it's a reasonably priced, high image quality option that I'm sure others here have done. Load 35 mm film into an RB67 film back, and Bob's your uncle, 35x67 sprocket hole panoramics with no further effort.
Of course, if you have a ProSD version film back, you pretty quickly discover that the frame counter doesn't advance, and you're left either guessing the right fraction of a lever stroke or living with the frame spacing increasing (to nearly frame size) through the length of the roll as the wound film increases the spool diameter. The older ProS backs use the roller on the supply side to drive the frame counter, but the ProSD backs have a narrow additional roller on the mechanical end that does that job, so the 35 mm film won't drive the counter.
Then there's the fact you need a 220 back to handle 36 frame length 35 mm film, which is twice as long as a 120 strip. Good news and bad news, since with 220 out of production, these have dropped in price a bit. Also the wasted film at the start (about a foot to get from the cassette to the takeup spool) and end (at least three to as much as eight inches, depending exactly where your frames wind up on the roll), and the need to unload in a darkroom or changing bag.
So, picture being able to use the whole roll of 35 mm, no waste; dependable advance with the lever and consistent frame spacing throughout the roll, and working double exposure protection if you're ProSD enabled. No dancing with the double exposure lever just to be able to fire the shutter because the film back thinks the film hasn't moved. No unloading (and winding the film back into the cassette) in a dark bag.
You'll need three high-tech pieces of kit: a couple sets of 35mm to 120 adapters (two knobs each, one for each end; these 3-D printed items are a few dollars per set from multiple sources), a couple lengths of 35 mm leader (fixed-out film works, or you can buy movie leader) cut to the header and tail lengths you need, and two bulk-loader cassettes (the leader and cassettes can be duplicated for multi-roll shoots, the adapters don't need to be). Plus a couple inches of black electrical tape.
Start by putting a single wrap of electrical tape around the counter drive roller, if you have a ProSD 220 back. This will let the film drive the counter (the film doesn't ride this far over, so the extra thickness won't change frame spacing).
Load the film into the cassette with the shorter leader piece (I'd recommend eight inches -- long enough your last exposure gets protected, short enough you don't often shoot the best shot of the roll on the tail leader) first, then film taped to the leader, the usual five feet of film for a 36 exposure roll (which should give about eighteen exposures in a 6x7 back), and a leader as long as the lead-in on a 120 backing paper, with a mark where the start arrows are. Then attach the free end of the leader to the spool in the second cassette (be sure to mark the take up cassette so you don't try to load backward).
With the adapters on both cassettes, the film will stay centered in the gate, allowing precise composition (you can also make up a composition mask for the viewfinder, if so inclined), and you can load just about like loading 220 film. The 120 adapters mean the film back securely holds the cassettes, no fumbling around like with a loose cassette. Once the roll is done, the last exposure will have wound into the takeup cassette, and you can unload in the light. If you're shooting a lot, you can carry multiples of these assemblies and reload in about the same time it would take to load 120 or 220 film.
if you like a wider ratio, you could even make up a frame mask to go into the film back behind the dark slide. Since the film is always in the same place, between the two cassettes, a correctly dimensioned mask will cover only the sprockets and give a 24x67 frame.
Now try not to faint when you look at the prices for a 35 mm fisheye for your RB (I do plan to get a 50 mm, though).
Of course, if you have a ProSD version film back, you pretty quickly discover that the frame counter doesn't advance, and you're left either guessing the right fraction of a lever stroke or living with the frame spacing increasing (to nearly frame size) through the length of the roll as the wound film increases the spool diameter. The older ProS backs use the roller on the supply side to drive the frame counter, but the ProSD backs have a narrow additional roller on the mechanical end that does that job, so the 35 mm film won't drive the counter.
Then there's the fact you need a 220 back to handle 36 frame length 35 mm film, which is twice as long as a 120 strip. Good news and bad news, since with 220 out of production, these have dropped in price a bit. Also the wasted film at the start (about a foot to get from the cassette to the takeup spool) and end (at least three to as much as eight inches, depending exactly where your frames wind up on the roll), and the need to unload in a darkroom or changing bag.
So, picture being able to use the whole roll of 35 mm, no waste; dependable advance with the lever and consistent frame spacing throughout the roll, and working double exposure protection if you're ProSD enabled. No dancing with the double exposure lever just to be able to fire the shutter because the film back thinks the film hasn't moved. No unloading (and winding the film back into the cassette) in a dark bag.
You'll need three high-tech pieces of kit: a couple sets of 35mm to 120 adapters (two knobs each, one for each end; these 3-D printed items are a few dollars per set from multiple sources), a couple lengths of 35 mm leader (fixed-out film works, or you can buy movie leader) cut to the header and tail lengths you need, and two bulk-loader cassettes (the leader and cassettes can be duplicated for multi-roll shoots, the adapters don't need to be). Plus a couple inches of black electrical tape.
Start by putting a single wrap of electrical tape around the counter drive roller, if you have a ProSD 220 back. This will let the film drive the counter (the film doesn't ride this far over, so the extra thickness won't change frame spacing).
Load the film into the cassette with the shorter leader piece (I'd recommend eight inches -- long enough your last exposure gets protected, short enough you don't often shoot the best shot of the roll on the tail leader) first, then film taped to the leader, the usual five feet of film for a 36 exposure roll (which should give about eighteen exposures in a 6x7 back), and a leader as long as the lead-in on a 120 backing paper, with a mark where the start arrows are. Then attach the free end of the leader to the spool in the second cassette (be sure to mark the take up cassette so you don't try to load backward).
With the adapters on both cassettes, the film will stay centered in the gate, allowing precise composition (you can also make up a composition mask for the viewfinder, if so inclined), and you can load just about like loading 220 film. The 120 adapters mean the film back securely holds the cassettes, no fumbling around like with a loose cassette. Once the roll is done, the last exposure will have wound into the takeup cassette, and you can unload in the light. If you're shooting a lot, you can carry multiples of these assemblies and reload in about the same time it would take to load 120 or 220 film.
if you like a wider ratio, you could even make up a frame mask to go into the film back behind the dark slide. Since the film is always in the same place, between the two cassettes, a correctly dimensioned mask will cover only the sprockets and give a 24x67 frame.
Now try not to faint when you look at the prices for a 35 mm fisheye for your RB (I do plan to get a 50 mm, though).