Mamiya 6x7 pinhole ideas

[JeffVanderlip]

Hi Everyone,

I am new here. I have been reading the forum for a few weeks now. Some great stuff. I have been photographing for nearly 45 years. My best friend and I had a darkroom together when we were teenagers. We still get together every year and take photos. I started thinking about a Christmas present (now birthday present ) for him and thought I would make him a pinhole camera. We played with pinholes many many years ago...used photo paper and Quaker oatmeal boxes. Got some OK shots. We both started shooting digital a few years ago, but we still both miss film. I thought a pinhole would give him a new technique to use in his craft.

I have bought a pair of Mamiya 220 pro 67 backs (I am going to build my own pinhole too!)...I like the idea of a well behaved film transport. I am working out all the interlocks...still waiting for some 120 film in the mail to run a roll through and see what does what. Still trying to nail down what tells the back to allow the film to advance a frame. Can anyone tell me any details on how a Mamiya back works exactly? I suspect the release is the center shaft of the advance drive post that extends toward the camera.

I also bought some 0.2mm pinholes (was planning on buying from Earl, but got impatient getting access on here and just grabbed some on e-bay). Thinking about a 25 to 30 mm focal length. I have done some rough calculations and it seems a manual shutter might work...thinking 100 ASA (ISO) film. Am I correct or do I need to try and get some type of faster shutter.

Also, if I do go to a manual shutter, any recommendation on what the best (most robust) design types are?

I also plan on making the pinhole able to rise and fall...like the idea of being able to get some perspective control.

Anyways, those are my thoughts but I would love some feedback from some of you folks who have built these already.

Thanks for reading!

Jeff

[MartinS]

Hi and welcome here!
I have no experience with the Mamiya backs but I think someone here could help. As for the shutter, I have tried out several "types", and from my point of view, I would recommend a "lens cap shutter" (i. e. using a filter ring attached around the pinhole ad regular lenc cap of suitable size), or a "magnetic shutter" which is a common refrigerator magnet used to cover the pinhole. In both cases, I would recommend the "shutter" being rather bigger, so you can remove it just a bit (letting the camera field of view still obscured by it), wait a second or two for the camera to stop shaking, and then move it off quickly without touching the camera.
I like the simplicity and reliability of them, especially when used in combination with a film back which itself has a dark slide. There is no danger of accidental exposure during camera transport in case the shutter falls off since the dark slide secures the film. Shorter exposures are a bit harder to perform; however, with the 100 ASA film and the f/150 you hardly get to less-than-second time range.

Regards,

Martin

[Doug K]

You've seen many different opinions here regarding pinhole cameras. Some folks like the simplest thing possible, and others get quite complex with their construction. I tend to choose a middle ground, and try to use well made parts to construct mine. I convert old cameras found on ebay for cheap to pinhole. My requirements are a bulb setting on the shutter, a connection for a cable release, and 120 film. The Voigtlander Brillant makes for a nice pinhole camera since it's a TLR, and you can frame the photo with the viewing lens. You can find old shutters on ebay which you can easily adapt to pinhole work. I've been able to make mounts out of brass that fit in where one of the lens elements sat using the old split ring to hold it in place. On my Brillant I used the aperture ring to mount the pinhole. The problem with using old cameras is you're somewhat limited on focal length. I do have a wide angle pinhole camera in the works using an old folding camera with the bellows removed, but I haven't finished that one yet. I would think you could easily make a box to mount your film back, and have some sort of lensboard to mount a shutter. Ideas abound on this site, that's for sure. Welcome here, and have fun!

[JoeVanCleave]

I don't have experience with RB67 backs at all, but here's a link to some info. I'm sure an Internet search will find more. It appears there are different generations of bodies and backs, the Pro, Pro-S and Pro-SD. The original Pro back doesn't have multi-exposure protection, for instance. The Pro-S has improved film flatness (not important for pinhole) along with double-exposure interlock and darkslide interlock (can't pull the darkslide unless attached to the body). The ProSD body adds mechanical light traps instead of foam.

There's also something in that link about a rotating interlock plate that fits between the film back and body, that not only provides film back rotation but operates some of the interlock features.

I know with my Bronica ETRS film back I am able to defeat these interlocks mechanically by inserting pins or other mechanical contrivances into the interlocking mechanism, I'm certain you could figure out how to do it with the RB67 back, if they're strickly mechanical in operation.

Regarding shutters, I've built ones that rotate about a central pivot point, guillotine-style ones that slide up and down, and simple lens-cap shutters. They all have their advantages and disadvantages. During transport, you want a shutter mechanism that resists being accidentally dislodged. Guillotine shutters are good in this regard. But if they are rather snug, the camera can vibrate when opening the shutter, which can blur the image if the exposure time is just a few seconds long. In this regard, lens cap shutters are better. My last several cameras have used rotating shutters, and I find them about as good as guillotines but simpler to make. I agree with Martin that having an oversized lens-cap style shutter would be an advantage, permitting you to let the camera vibrations settle out before making the exposure. I do this as a matter of course on large format glass lenses cameras, if the shutter speed is multi-seconds long.

Good luck and keep us posted of your progress.

~Joe