expanding back from camera ( small ) to mate with back ( bigger )

[jnantz]

is there any best way to make a adapter that
can mate a larger back to a camera?

i figure its "whatever works works" but maybe
there is a best way to do it ...
does the adapter have to be a certain distance from the camera
to assure it won't crop the negative ?

thanks !

[Bob Salomon]

is there any best way to make a adapter that
can mate a larger back to a camera?

i figure its "whatever works works" but maybe
there is a best way to do it ...
does the adapter have to be a certain distance from the camera
to assure it won't crop the negative ?

thanks !

You have other problems to figure out. Will the lenses from the current camera cover the larger format?
Does the current camera have a long enough bellows draw to use with lenses for the larger format?

[jnantz]

hi bob


i've got that all covered. they are both the same format
the lens and bellows have no issues either.

thanks

john

[Michael Roberts]

John, see ideas in this thread: http://www.largeformatphotography.info/forum/showthread.php?120318-fabricating-wooden-camera-backs-reducing-backs-expansion-and-enlarging-backs&highlight=11x14+expansion+back

Yes, your larger back will have to be a certain distance to avoid vignetting--less so for shorter lenses, more so for longer lenses...

[Tin Can]

Draw triangles on paper to visualize what you need, then a little geometry will get it exactly.

It's fun 'homework'.

[jnantz]

michael and randy,
thanks !

i'm not really going from a smaller format back to a bigger one or visa versa ..
they are both the same format, even made by the same company! but
because they are different models, the backs connections are different
it seems to be a few cm off so the back and the camera won't "mate"
its kind of like trying to use a 5 3/4 square lensboard on a camera that takes
5 5/8 boards, close enough to look like it might fit, but big enough to be annoying.

john

[Bill_1856]

I use a 5x7 extension back on my 4x5 Nagaoka. Works beautifully, but any lens longer than 210mm cuts off about 1/2" on each side, giving a 5x6.5. (Just like Paul Strand).

[Drew Bedo]

The issue is not entirely clear to me. I am guessing that the "smaller" camera is complete except for a GG back, while the available GG back is for a similar camera of the same format, but it is a different model with different dimensions. Perhaps this adaptation should be done by a professional camera shop.

Or maybe something involving a lot of gaffer's tape.

[jnantz]

thanks drew.
i am not affraid of tape ...
typically i use WIDE black masking tape
to attach a roll film adapter to my graflex slr,
and make box cameras, barrel lenses and paper holders out of board and ... tape ..
and currently have a 11x7 back attached to something using masking tape :)
i was thinking last night and if i could make some sort of large bead of a DRY doughy substance
that i can use as a big gasket .. that will get hard and form the light trap and mate the 2 backs together
( and be removed when i want to use something else on the camera ) i would use that in a heartbeat ..
i was thing of that doughy-stuff i made a relief map of the USA on a sheet of cardboard when i was in grammar school
no idea what it was, or if it is too "wet" to mold on the back of a camera and camera back but
it is just something like a step-up /step down ring i'd need ... maybe i can find some memory foam, wood putty ?
seems less "goey" ...
i'd rather not get a professional involved i like ramen noodles but not enough to eat them for a year.

john

[Randy]

I had a 5X7 back from a different 8X10 camera I wanted to mate to my 8X10 camera (it was a tad larger). I had a carpenter friend plane it down to the exact dimensions as my 8X10 back - took all of about 30 minutes for him to do it. I took it home, painted the now bare wood matte black, replaced the corner pins (that set in the camera rear standard holding the back in place) and it was ready to go. I could have done the work myself with a wood rasp but it would have taken a lot longer and probably would not have been as exact. This may not be the information you need though...

[jnantz]

thanks for the suggestion randy
but i would rather not do something irreversible ..

[Michael Dodd]

Foam core and tape????? Cut foam core to make your adapter seal with tape. will it be strong enough to move a film holder??

[jnantz]

thanks michael
i was thinking of pumbers putty ( dense hard putty that doesn't dry out ) but this morning
i had an epiphany and now i am leaning towards corrugated cardboard
it is more rigid than foam core and easy to make an adapter just like
you described :) i have extra box board from a stalled corrugated cardboard camera case
i started making last spring but didn't manage to finish.

[Drew Bedo]

What about that black rubbery liquid stuff they sell on TV?

Or the aerosol foam gap filler (also sold on TV)?

[jnantz]

i thought about that stuff too, but worried it would acutally be permanent or hard to remove
i'd like to keep using the camera with a variety of backs, and the back ( i am trying to double duty )
with the camera it originally came with. if i had a random back and a camera to afix it to permentantly
i wouldn't hesitate to use that rubbery or goopy stuff. i was also thnking of that stuff they use inside
head-neck yokes so you can sleep on a plane/in a car...

[Drew Bedo]

Think about this: First off apply furniture wax to the wood, "Mask" off the wood parts with heavy food wrap film. Pieces of wide masking tape may have a part to play some how too.

Somebody else with real-world experience please chime in here. I would hate for him to wreck a fine camera just on my coffee-driven ravings.

[jnantz]

no worries drew
i think i have settled on a cardboard adapter i make by hand. it willbe stiff enough
i'm used to working in cardboard anyways, and its kind of funny after making cameras, backs paper holders and all sorts
of other stuff out of cardboard, i never thought of making a splayed back out of it too.

[jnantz]

well, its been 5 months and i never finished this project.
it's added to the list...


thanks again for your inputs, and in case anyone else has a centuray 8 and thinks a century empire state will fit it
it won't ...

[Harold_4074]

John,

I wish I had seen this thread when it was current. If I understand your problem, you want something to fill the space between the components and sort of "key" them together--reversibly. The other day, I was in a TAP Plastics store and saw what I think was an addition-cure silicone putty. This is pretty much the same thing that dentists use for precise impressions, and I have used the metrology version for making otherwise awkward measurements of mechanical parts. It is a two-part system that you knead together into a fairly stiff putty; if you made a temporary dam out of cardboard, you could fill a channel, press the two camera parts together, and then trim the resulting "spacer". The putty is nontoxic (duh...), doesn't seem to stick to anything, and being an addition-cure polymer doesn't release acetic acid or anything else as it cures.

Good luck!

Harold

[LabRat]

Hi John!!!

Expansion backs are made for different cameras, but the big downside is that if you use the rear movements, they will be way off axis, throwing off that feature... Field cameras are usually not really strong on the rear, and the extra cantilevered weight from the extension + handling forces on the rear creates strain there...

I think the wise way to do this is to think of the Sinar middle standard scheme, where the camera rear would have a MS adapter connected to a bellows, that would extend to the larger back, and all this would ride on a monorail so the different stages could be moved where they would work well, so they will be well supported, individual stages could have their own adjustment, and the whole rig can be balanced well depending where the tripod makes connection to the common monorail adapter... Not the cheapest way (as you are basically adding another camera rear to your camera), but can maintain all functions if done right...

If you install a larger box behind your camera with the larger back, that could work... (Using the existing baffle step/mounting pins would not need tape/glue/sealants , just clip on...)

There are other ways, including just getting a larger camera, but with some excess of camera junk around???

Muse, muse, muse...

Steve K

[Michael Roberts]

John, precise measures would help inform possible solutions. For example, if I understand your problem, you've got something like an 8x10 camera back that's 11 1/2 inches square and a back that's 12 inches square. You don't want to permanently modify either one.

If this is the case, I would fabricate a "step-up frame" out of 1/4 x 1" basswood. Make an inside frame 11 1/2" o/s dimension to mate with the camera and attach with pins or whatever is needed to mate with hardware that is already on the camera so that the frame is removable. I would glue a 12" o/s 1" x 1/4 frame to the outside of the first frame (overlapping by 1/2 inch) and install hardware on it to mate with the back you have. No changes to either camera or back.

Finish the frame out by gluing in strips of 1/8 x 1/2" basswood for light traps, as needed on both camera and back sides. Paint the frame flat black on the inside.

Materials and tools needed: basswood strips and brass strips and screws, available at a good hardware or craft store; a mitre saw to cut the wood square on the ends; an 18 inch steel ruler; wood glue; a right angle to glue the wood frame against and hold in place until dry enough to move (just a couple of minutes). Oh, and your time, of course, which is what most of us are short of.

Bottom line: if you've got a wooden camera and a wooden back then I would make an adapter out of wood and use similar metal hardware. I wouldn't try anything as flimsy as putty or foamboard and tape. My two cents.

If this seems like a workable solution and you need help with it, let me know. I'll be glad to help out.

[jnantz]

harold, steve and michael
i appreciate your suggestions for my camera.
now that the weather is getting warmer, maybe i'll start work on figuring this out ...

thanks again for your advice !
john