Enlarging Back (as opposed to reducing back) Project

[Fragomeni]

Hi everyone. I'm already in progress with this project but I wanted up post a thread to see if anyone had anything valuable to offer. I'm building an enlarging back for my 8x10 Deardorff. It will function much like a reducing back but will expand the capacity of the camera to 11x14. The back will attack to the rear standard in the same way that a typical spring back would and will either be a tapered box to which an 11x14 spring back will attach (however I have concern about weight) or it will be an 11x14 frame (possible rear standard) with a second set of bellows that connects to the rear standard in the same way. Struts would be used to collapse the back and when fully extended would keep the back parallel where it belongs. This option would also reduce weight. There may or may not be a support arm to support the extra weight on the rear standard if necessary. I'm wondering if anyone here has done this and if you can offer any insight. Thanks for the help.

[Michael Roberts]

http://www.largeformatphotography.in...ght=11x14+back

[Fragomeni]

Thanks Michael!! Steve and I have communicated in the past regarding some of his other projects but I didnt know he made one of these. I've PMed him. Thanks again for the link. Much appreciated!

[Michael Roberts]

You're welcome; glad to assist. I have done some thinking about this, too. My ideal design would be a collapsible expansion back--where the sides would fold in for easy storage/transport and fold out to fit into a rigid frame when needed to connect to the smaller camera back. Still trying to work this out in my head. I'm thinking the basic material would be wood, obviously would need hinges to connect to the larger rear frame, plus a liner of black-out cloth--sort of like a bag bellows inside a fold out wood frame. And I would want the sides, top and bottom to be tapered. The part I haven't quite worked out is the connection to the smaller camera back. The frame to connect to the smaller camera would be easy, but how to connect the fold-out sides, top and bottom of the expansion back to the connecting frame? Need to think some more about this.... Rigid expansion backs, like Steve's in the link above, work great for shorter lenses, but for longer lenses you need around 12 inches of distance from the smaller back to the film plane of the expansion back, and that starts to get unwieldy to haul around in the field (okay for studio and working outdoors near your vehicle, though). A collapsible back would solve that problem, but presents it's own problems....

I guess another possibility would be folding metal struts between the expansion back and the connecting frame, as you suggest, with a bag bellows in between....

In addition, with a lengthy expansion back, I think you are right that it would be a good idea to design the back to allow a supporting arm to a tripod leg or else a tripod mounting nut under the larger back to allow a monopod or second, lightweight tripod to be used for additional support.

I also think it's a good idea to try to plan ahead by thinking about the focal lengths of lenses you are most likely to be using. If, for example, most of your work will be done with shorter lenses, then you might be able to get by with a shorter, rigid expansion back light Steve's. Then, for the occasional longer lens, you could have a separate spacer like this:

http://www.largeformatphotography.in...7x11+expansion

For your weight concern, I have been working with balsa wood, which is extremely strong for it's weight, with a covering of 1/16 inch basswood to protect the soft balsa wood.

[Tom Keenan]

11 x 14 B&J Frame
Tom Keenan

[Fragomeni]

Michael, you bring up a number of good points. I've found the struts that I thought I'd use but I need to figure out if they'll be strong enough to support the extended back. I planed to attach two struts to the top, bottom, and both sides. Tom has the extra rear frame (pictured above) which should be sent my way as soon as he invoices me and I pay for it. I'll use this frame to which the spring back will be attached. I've just ordered replacement hardware so that everything goes together smoothly. If the struts and bellows idea doesn't work I'll probably just make it a rigid extension with tapered walls to extend it out and up to 11x14. The balsa wood covered in basswood sounds like a good plan and I'll probably try that. It sounds like a much better idea then using the heavier hard woods I planned on using.

[Fragomeni]

Oh, your spacer back in the link looks fantastic and looks very well done. Can you tell me how much it weighs with the spring back attached? I figure you're spacer back is 2 inches and weighs 1/2 a pound so if weight correlated to the extension then a 10 inch (about how much extra extension I intend to add) spacer would weigh 2.5 lbs plus the weight of the spring back which isn't much. I'm thinking about how well the rear standard of the camera would support that. Hmm.

[Michael Roberts]

yes, also factor in a 3lb film holder inserted into the spring back. So, that's why I think a monopod or lightweight tripod or tripod arm could be useful.

your calculations seem right to me. The weight of the 11x14 spring back will depend on the brand. The only ones I have on hand are a balsa/basswood I made and an 1899 ROC King which is also unusually lighter in weight, so I don't think those weights will compare to your back if it's a Deardorff or B&J.

[Michael Roberts]

I planed to attach two struts to the top, bottom, and both sides.

Francesco--You might think about attaching two struts each to the sides--might handle the weight better. Struts on top and bottom will be forced to support weight only with the thinner parts of the metal.

Oh--keep in mind my spacer is 11 and 1/2 inches square. So increase the weight for 16 inches needed for 11x14.

[johnielvis]

i started off doing something like this---expansion back to my 8x10---after figuring out the lenses I wanted to use and the rest of the bs, I determined that it's best to just make a whole 11x14 camera---particularly if you want to use longer lenses or extensions---the way I was going to use it, my 8x10 would have ended up being nothing more than a heavy complicated front standard---

if you have aback, then you're better off building a complete camera---simple boxes will do--and a LARGE lensboard up front.....OR---if you can use the BACK of your 8x10 as a FRONT standard to an 11x14---then you'll be in buisiness---i toyed with that as well.....BUT....long story short--now i got 3 11x14's....each with it's own purpose depending on application---lens extension you want to use makes a BIG difference on camera design with thiese bigger formats---even 8x10 is getting a bit awkward extension wise when it comese to the longer lenses or close-closeups. The extension back will not allow longer lenses or closeups without getting vignetting---and movement will be severely limited--

just my experience----take it with as many grains of salt as you want.