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Hallo, I'm in process of building a 5x7 folding camera and have a few questions regarding the bellows construction:
What is the difference in bellows properties between a bellows with wider and less in number folds vs. bellows with narrower and therefore numerous folds?
What is the width of a typical bellows fold of 5x7 cameras?
Do any of you have a recent find of new (and better) bellows material on the market?
Thank you in advance for all your help!
http://www.cyberbeach.net/~dbardell/bellows.html
You might find this helpful.
Seems to me the bigger the folds the smaller the compression but the smaller the inside clearance.
Regarding your first question - except for bag bellows or wide angle bellows greater number of folds gives you greater flexibility of the bellows (and sometimes a greater possibility of bad folding if closing the camera too quickly, just a side effect). Also - less folds means greater space taken by the folded part (for the same lenght). The dimension the fold depens on how long you want to have the bellows. Best if you play with paper folded as you see on one side of the bellows to see different solutions for a different length - you can also draw it on a piece of paper in 1:1 scale to see the changes and the needs for the required lenght.
gps:"Also - less folds means greater space taken by the folded part (for the same lenght). The dimension the fold depens on how long you want to have the bellows."
I don't follow you on this. The wider the pleat, the fewer the folds, and therefore the less thickness when folded (i.e., it will compress more to a smaller minimum extension). I just built a square bellows with 1" pleats and it compresses to under 2". (Folded thickness is 2" in the corners where the material overlap is doubled due to the corner fold, and 1 1/4" in the bellows center.) A diagonal seam also facilitates maximum compression.
Andrey:"What is the width of a typical bellows fold of 5x7 cameras? Do any of you have a recent find of new (and better) bellows material on the market?"
For 5x7 and smaller bellows I believe the figure I've seen is 5/8" for bellows pleats. Many larger bellows utilize a 1" pleat.
I used a black pseudo-suede 150 denier nylon from Outdoors Wilderness Fabrics for the interior lining and the better grade Porter's Darkroom Cloth, a rubberized nylon, for the bellows exterior layer. Both Porter's and OWF have websites.
Joe, you mean the thickness of the folded bellows - I meant the dimension of the zig-zag part (the triangle seen from a side). It's not always clear when you make verbal description of geometry, sure.
Ya'll find some more information here http://www.geocities.com/diannebest/bellows/bellows.index.html
Hallo Calamity Jane, Which type of Roc-Lon Blackout Linings did you use? There is so many on their WEB site. And second: They are all white or ecru color. Are your bellows white or you covered it with something else?
Thank you once again to all of you! Your posts are truly helpful!
I am not even sure - it is whatever the local wholesaler had in stock - probably the "economy blackout".
Yes, it is off-white on both sides. However, ordinary flat black spray paint sticks to it well.
All my bellows consist of one layer of Roc-Lon blackout material with about 0.010" aluminum stiffeners - no inner liner - sprayed black afer fabrication.
Think maybe my next bellows will be black inside and pink outside ;-)
I have in hand a custom-made bellows for a 5X7 project camera that was made by Camera Bellows
in the UK. Perhaps a description will help. (This bellows will be used in a "stretched" B&J
Press camera.)
The outside dimensions are: 8 1/2 X 6 5/8 tapering to 4 1/4 square. (inches) (Inside dimensions of the frame are 5" X 7".) The bellows wrap around frames on front and back which are 1/16" thick each and are included in the thickness collapsed at only 3/4". Fully extended the bellows are over 16" (but the camera itself only goes to about 12 1/2" or so.)
There are 13 & 14 folds which are 5/8" wide.
The corners are not square but at 45 degrees (truncated.) The material of the bellows is very thin synthetic material on the outside and black cloth on the inside. Of course making a
bellows that collapses to a very thin dimension is easier with a tapered bellows design. The
truncated corners also help also.
The dimensions of the bellows described above were governed by the adaption to a stretched B&J
Press camera. If I were to build a 5X7 folding camera from scratch the internal dimensions
would be somewhat larger to cut down on the potential of "bellows flare."
Camera Bellows wrote me while processing my order saying they were having some difficulty with
the material supplier- which is interesting in itself considering the problems hobbists have
finding suitable materials.
Finally, I am very grateful to have information about a source for bellows material. It seems
that up to now the sources were almost trade secret! Going to try my hand at making a bellows for
a new 7X17 project camera- some day that is.
In many ways I find the making of a bellows to be every bit as rewarding as making a camera - more so in many way.
With a tapered bellows, ending up with a good result means doing a LOT of things properly, a lot of things that are very similar but slightly different.
I think there are around 396 stiffeners in my 4x5 bellows, all the stiffeners are in pairs, so there's 198 pairs of stiffeners that are all slightly different sizes. It's challenging to do the same thing 396 times without screwing up at least one of them!
I have been using AutoCAD to do the layout which simplifies the layout and keeps it accurate.
Of course, by the time you have glued up 396 stiffeners with contact cement, EVERYTHING is covered with contact cement! ;-)
Good luck Bob - you'll enjoy it!