RB67 on 35 mm

[Donald Qualls]

Of course, the other reason to use a 220 back for 35mm pano in an RB67 is that it will let you shoot 20 frames, which is all you'd get on a 36 exposure roll anyway (if loaded with leader and trailer). The 120 backs stop spacing the frames at 10 (though if you're doing the double exposure lever dance that isn't a limit -- I wrapped tape on the roller of my ProSD 220 back so the 35 mm film drives the counter and spaces correctly).

 

[Ariston]

Of course, the other reason to use a 220 back for 35mm pano in an RB67 is that it will let you shoot 20 frames, which is all you'd get on a 36 exposure roll anyway (if loaded with leader and trailer). The 120 backs stop spacing the frames at 10 (though if you're doing the double exposure lever dance that isn't a limit -- I wrapped tape on the roller of my ProSD 220 back so the 35 mm film drives the counter and spaces correctly).

Good point. I didn't think of this because I use the double exposure lever from the very beginning so I don't lose frames at the front of the roll. I tape my roll to a used 120 paper leader (just the leader) and am able to shoot the whole thing.

 

[Donald Qualls]

If you tape the roll where the film would start (or overlap by a couple inches, to allow for the film that was out of the cassette) and load to the arrow, you get that automatically from the film magazine's start. It automatically advances to give about half to 3/4 inch of blank film before the first frame on 220, and 120 and 220 have the same leader length, AFAIK.

 

[Oxleyroad]

I like this idea, and now I have a use for my old RB67 220 film backs!

 

[Jeremy Mudd]

OK, so given the crappy day that it was here on Sunday and the fact that I needed to force myself to do something photo-related, I shot 2 rolls of Kodak Pro Image 100 35mm film in my RB67 ProSD. 1 roll in the 220 back with adapters, and 1 roll in the 120 back with adapters. I had the double-exposure switch flipped on both so there was no issue of not getting all of the shots in on the 120 back.

I shot the same shot each time with each back without changing or moving anything. The nice thing about the overcast and drizzly day was that the lighting wasn't changing. I varied things up with close focus, far focus, and wide open. Different subjects. All shot with the 180mm Sekor C f/4.5 lens. Both rolls were developed at the same time in a Paterson tank with UniColor C41 chems. Scanned on an Epson V600 between two pieces of ANR glass, at 48bit color, masks/ICE off, 3200dpi. Note no dust-removal or post-processing has been done on these.

I've scanned the first few images, but haven't ran thru all of them yet. I'll report back with a more in-depth analysis, but my initial take-away is that the two are fairly close in terms of sharpness. I *might* give the nod to the 220 back slightly, at least in the case of this first image shot at f/8. But its so close.

More to come.

First image is the 120. Second is the 220. First crop is the 120. Second is the 220.

 

[Donald Qualls]

To my eye, not so much a difference in sharpness, but a very slight difference in focal distance. The lower image is focused a little closer to the lens, which would equate to the film being about a gnat's whisker further from the lens. I don't think it's enough to matter unless you're shooting macro or doing wide open portraits that will be printed HUGE.

 

[Alan Edward Klein]

Yes. Many more cropping opportunities shooting full frame 6x7 (or whatever) and cropping to panoramic aspect ratio. No question.

However, part of the fun of shooting 35 mm in a medium format camera is being forced to compose for the aspect ratio, instead of being able to crop from the full frame. It's a discipline, a creative limitation. Some of the same idea as shooting a 1930s vintage box camera instead of your fully adjustable folder (that uses the same film and format). Or shooting in the "Lomography" class for creative purposes.

For me, it's something I can't do well with other equipment I own or can afford. With the 35 mm RB67, and a 50 mm lens, I'll get results very similar to an XPan with a 45 mm lens -- for less than the cost of the lens.

Dan, the 90 mm and even 60 mm lenses for 4x5 would do a nice job on 35 mm in a 120 roll holder (film back, as opposed to the ground glass back, I suppose) -- they only cost about twice what my whole RB67 setup has cost so far. I can get a 65 mm lens for under $200, apparently; 50 mm are a bit more, but still within reach. Not many fisheyes that will cover large circles, though I think I've seen at least one 4x5 camera made to use only a proprietary fisheye.

Don, can't you mark up the viewfinder with a grease pencil or masking tape to show where the 35mm film would be to help frame the picture? As an aside, I recall seeing some overlay in one of the editing program where you can overlay the sprockets on 120 film as if you shot 35mm. I forgot where I saw it.

 

[Alan Edward Klein]

What I wanted to indicate is that sprocket holes at the rebate are one thing, them being cluttered with letters, figures and barcode another thing. Which to me decreases the choice of films for this kind of exposure.

Typically these sprocket-holes pananoramas are cluttered with rebate signing, up to barcodes.

While this is a 35mm shot on a 35mm, it really shows the mess that was in the rebates of Ektachrome years ago. They even added "Processed by Kodak" in the rebates. I don;t know if the new Ektachrome is the same.
Blue Tang by Alan Klein, on Flickr

 

[Alan Edward Klein]

No barcodes back then 30 years ago.

 

[Donald Qualls]

If that edge marking bothers you, I guess you could buy Vision3 movie stock in 400' rolls and roll it down yourself (or get it from resellers who put it in cassettes -- IIRC, Cinestill even removes the remjet before sale). AFAIK, the movie film only has the actual film stock ID every few inches, no frame numbers (and certainly no "Processed by" tag, that was presumably added by a Kodak processing machine after the camera exposure).

 

[Alan Edward Klein]

If that edge marking bothers you, I guess you could buy Vision3 movie stock in 400' rolls and roll it down yourself (or get it from resellers who put it in cassettes -- IIRC, Cinestill even removes the remjet before sale). AFAIK, the movie film only has the actual film stock ID every few inches, no frame numbers (and certainly no "Processed by" tag, that was presumably added by a Kodak processing machine after the camera exposure).

But the Processed by Kodak makes it so much more valuable. It's like buying an old Mickey Mantle baseball card with Mickey's signature. It's cool man.

 

[Donald Qualls]

But the Processed by Kodak makes it so much more valuable. It's like buying an old Mickey Mantle baseball card with Mickey's signature. It's cool man.

Well, that depends on what Mickey signed it, I guess -- was it actually Mickey Mantle? Or was it Mickey Dolenz, Mickey Mouse, or Mickey Finn?

 

[Alan Edward Klein]

Well, that depends on what Mickey signed it, I guess -- was it actually Mickey Mantle? Or was it Mickey Dolenz, Mickey Mouse, or Mickey Finn?

Well if Mickey Mouse signed it, I'm sure it would be worth more than if Mantle signed it.

 

[Jeremy Mudd]

I'm going to revisit this post.

On the RB67 Facebook group there were questions about shooting 35mm in an RB67 and I mentioned that there were differences in using a 120 versus a 220 back and some, ahem, let's say "overly enthusiastic" person posted some deroggatory comments saying I didn't know the inner workings of a camera and that the pressure plate put the film in the same plane no matter what back was used.

Part of me thinks that makes sense, then part of me thinks that based on the scans I posted and others I have at home there are slight differences.

Thoughts?

Jeremy

 

[AgX]

that the pressure plate put the film in the same plane no matter what back was used.

Part of me thinks that makes sense.

That is the way a pressure plate is designed for. Basically.

However then the idea came up to counter warping of the film around its longitudinal axis by not pressing the film directly onto the rails, but to rest the pressure plate instead on the lateral-guidance rails, or respective studs at same location. These got a height so that a slit is formed between the pressure plate and the primary rails, wider than the film-thickness. The play the film has in this slit was experimentally established to yield best averaging out of the warping into a more shallow wavy curve.
Of course a design may make this slit adjustable for film with and without paper backing.

 

[Donald Qualls]

Of course, the other question is whether the thickness of 120 backing paper is actually significant to the focus quality. I have a hunch it will make more difference with a wide lens (like 65mm or 50mm) than with a "normal" 90 or even longer 127, 150, 180 -- despite the shorter lenses having broader depth of field, we're now on the other side of things, and 0.2 mm is a bigger fraction of 50mm focal length than of 150mm.

 

[reddesert]

Depth of focus at the film plane depends just on f-number, regardless of focal length. This is because the beam emerging from the back of the lens to the film is a cone with length / diameter = (focal length) / (aperture diameter) = f-number. Depth of focus = f-number * circle-of-confusion;. At smaller aperture (bigger f-number), the cone is narrower, so you can displace the film with less blur. Suppose your desired circle of confusion is 0.05mm and you shoot at f/4, the depth of focus is 4 * 0.05 = 0.2mm.

A corollary of this is that you might be able to compensate for 0.2mm of focus shift by turning the lens to the f/4 DOF mark.

I don't have an RB67, but I have examined the pressure plates for Mamiya M645 120 and 220 inserts, and there's a slight difference in the pressure plates - the 220 inserts are relieved so that the film sits slightly closer when the plate rests against the camera body rails. The way an RB67 back determines the film plane is different, I think.