Who give advice about stereo tailboard cameras?

[Steven Tribe]

My latest "final acquisition" is a tailboard german 13x18" reisekamera. Bought mainly for the universal iris mount that was attached. Underneath the grime was the delightful name Curt Bentzin Görlitz. I have just finished cleaning the brass and repairing the bellows when I noticed two central fixing slots in the back of the front standard (in the middle - top and bottom) and two matching slots at the back of the camera on the wood frame - just before the ground glass. These have obviously been there from day one as they are reinforced with brass.

I very much doubt wheither anyone here has the same camera - but this possibility for mounting a stereo adaptor may be common for other 5x7, 5x8 and 13x18cm tailboard plate cameras? Perhaps even the same system? I imagine that the front separating baffle must go quite deep into the bellows (length depending on lens image circle I suppose) - whilst the rear baffle can be quite a bit shorter. Or do they, perhaps overlap?

Any comments would be welcome.

[Ty G]

I am gonna hop in as an expert with stereo cameras. Yes, what you are saying about the slots in the front and the rear standards sound like they were for a middle "bellowed" septum. Most of the time, they were made just like the bellows. If it has the capabilities to do 5x7, 5x8, 4 1/2" x 6 1/2" then yes it most likely had stereo option. The only thing you didn't say was how big the lensboard is; as stereo cameras need a lensboard big enough (most of the time rectangle) to fit two lenses side by side usually at 3 1/2" or 4" apart depending upon the size of the plate.

[Steven Tribe]

Thanks for the info. I was afraid that stereo specialists had their own website somewhere else!

I enclose a few rough photographs. The total width of the "hole" on the lens board is 5". The slots have brass edges in towards the bellows so that it looks as is if there must have been compression in the central portion to keep it in place in use. The lens board is the slide across type - so perhaps it could use a single lens for landscape stereo photographs if there were accurate markings on the standard and board.

[Peter K]

The lens board is the slide across type - so perhaps it could use a single lens for landscape stereo photographs if there were accurate markings on the standard and board.
For stereo photographs the two optical axes - of the one or two lenses - should be only 65mm apart. So 5" is sufficient also for bigger lenses.

[Steven Tribe]

Thanks Peter. Curt Bentzin certainly knew how to make cameras - the brasswork details are tiny but wonderfully finished both front and back surfaces.

I forgot to mention that the brass reinforced cut out (one of four) can be seen in the 3rd photo.

[Steven Tribe]

Here is a very basic illustration of how I think the stereo accessory might have looked like! If would have been quite folded up when not mounted. The elasticated "ribbon" must be only be fixed to the folding edges - otherwise it won't contract and expand properly. Elasticated things don't last many decades so there not much chance of thesurvival of the genuine article.

[Ty G]

Peter, the 65mm measurement is important for the viewers, not the cameras. Yes, that number is supposed to be the average distance between eye centers, so this is important when making a stereo viewer. However, for the camera, distances can vary, depending upon the size of the plate. The more distance, the more stereo effect when viewed.

Steven, yes the sliding lensboard would allow a single lens to be used for the two sides of the plate (2 images). But, they weren't used for stereo images so much as they were used as multiplying cameras in a studio setting. If you have more than one person wanting an image or one person wanting more than one image, it is a lot easier and faster to process and expose one plate, then cut it in half.

[Peter K]

Ty, if the stereo pictures should have a "natural look" the distance between the lenses should have the same distance as the the eyes, 65mm. With bigger distances you will get an effect called "lilliputism", the subject appears nearer, and the relief is exaggerated. This was often used for table-top scenes etc. Also with "flat scenes" like arial images.

This is only valid for taking stereo-pairs with a "normal" focal-lenght, diameter of the image equal to focal-lengt. With longer taking-lenses the basis, normaly 65mm should be smallerto get the "natural look" too.

For big stereo-pictures, often used in photogrammetry, one needs a stereo-viewer equipped with mirrors or prisms to attanuate the long distances between the two centers of the two pictures to the eye-distance of 65mm.

[Steven Tribe]

As stereo lens sets are a pricey item (even the meniscus landscape sets), I'll think and try and use a single lens/sliding board system when the separation section has been constructed. The front standard has a lever release rather than a screw-in lock for the lens board. I do appreciate the response, Ty.

[Ty G]

You should have a blast and get very creative images. You can simply put a cardboard or wood solid septum attached to the rear standard. Make it so that when the camera is at min. focal length, the septum just comes short of touching the front. On the stereos I build, I do something similar using a solid septum about 4 1/2" long.

[Steven Tribe]

I have to make something that is attached to both front and rear standards unless I modify the existing fixing points. Using the rear alone would make for a loose septum I think. If there is interest, I'll post images of the bellows type stereo adaptor I will be making. I have the heavy paper, brass etc. I have realised that making a lens board about an inch longer will allow me to reach the extreme left and right positions without passing the velvet light seal which otherwise might pose a limitation. The design/profile of the top and bottom runners of the lens board are different.

[Jack Dahlgren]

Ty, if the stereo pictures should have a "natural look" the distance between the lenses should have the same distance as the the eyes, 65mm. With bigger distances you will get an effect called "lilliputism", the subject appears nearer, and the relief is exaggerated. This was often used for table-top scenes etc. Also with "flat scenes" like arial images.

This is only valid for taking stereo-pairs with a "normal" focal-lenght, diameter of the image equal to focal-lengt. With longer taking-lenses the basis, normaly 65mm should be smallerto get the "natural look" too.

For big stereo-pictures, often used in photogrammetry, one needs a stereo-viewer equipped with mirrors or prisms to attanuate the long distances between the two centers of the two pictures to the eye-distance of 65mm.

I've taken stereo photos out of airplane windows where shots are separated by hundreds of yards. Of course, I don't get a chance to point a 4x5 out the window, so I make do with an SLR and then align images in software later.

[Peter K]

I've taken stereo photos out of airplane windows where shots are separated by hundreds of yards. Of course, I don't get a chance to point a 4x5 out the window, so I make do with an SLR and then align images in software later.
This is the same methode used by aerial photographers for many decades, today also by satelites. If you know the speed of the plane and the time elapsed between the two exposures are taken, you can calculate the base. Together with the method introduced by Mr. Scheimpflug you can rectify the pictures to get a a map. ;)

Have fun

Peter

[Steven Tribe]

I have made a mock up of the separating central septum out of cardboard, elastic tape and bronze rods. Although I tested the elastic to about 2 1/2 times extension, I found that, realistically, about 2 times extension is about the limit. The system certain works, but getting a clean separation on the ground glass/film requires additional "engineering". I am leaning towards the thought of a 10cm long brass (mat black) fixed on the rear axis - with pure rubber (greater elasticity) to the front bar. Whether the bellows can absorb the reflected light remains to be seen.

The sliding lensboard system is certainly not friendly to objectives which have rear lens cells way past the flange thread - like petzvals, as I found out!

Sorry about the quality of the photos - but I think they serve as an illustration at least. The horrible glare was not on the ground glass!

[Peter K]

The sliding lensboard system is certainly not friendly to objectives which have rear lens cells way past the flange thread - like petzvals, as I found out!
You need a lens in "normal mount" and not in "sunk mount" as shown here (http://www.cameraeccentric.com/html/info/voigtlander_1.html) on page 8.

[Steven Tribe]

I think most petzvals with the rack and pinion drive won't approach the "normal" mount position - which means they stick back a lot. Most shutter designs will also cause problems. Lens board thickness is 5mm - whilst the thread of a smallish compound is 10mm (ring rather than flange) plus thickness of rear lens cell. I understand now why the Dagor 168mm the camera came with, was mounted in an iris mounting flange!

[Tim Deming]

Hi Steven,

I recently bought a 10x15 folding stereo camera, which was also missing the center septum. Mine (a Voigtlander) had 2 rings at the front (behind the lensboard) to attach the septum, but nothing at all to attach to in the back. The tight fit of the ground glass behind the bellows prohibited most anything mechanical from fitting there.

What I did was to construct a septum that looks nearly identical to one vertical side of the bellows, with hooks in the front. Since this "side of bellows" has jagged edges (or pleats, like the camera bellows) it is able to mate with the pleats on the top and bottom of the camera bellows. This allows it to expand and contract with the bellows without elastic, and it will also stay in place due to a small amount of friction (the septum is made just a hair smaller than the bellows). Although I need to find 10x15 film holders to try the camera out, it looks like it serves its purpose well.

Hopefully my description makes sense, if not I will try to find time to post a picture. If someone has an authentic example of one of these stereo septums, I would really like to see how it was supposed to be done!

cheers

Tim

[Emil Schildt]

As stereo lens sets are a pricey item (even the meniscus landscape sets)

hmm - not always..

MW classic had a few month about a dozen stereo lens pairs for sale..

Now only two left, but they are not (in my book) very expensive!

look here and scroll down a bit..

http://www.mwclassic.com/acatalog/Online_Catalogue_LENSES__ADDED__35.html

I am lucky enough to own one of the most besutiful stereo cameras I have ever seen...
Made by Louis Gandolfi a loooong time ago..

It also have slots for the septum, but the septum is also missing here...

It has a normal lens on a front plate (Dallmeyer stigmatic #4) and a lens board with a stereo set (Wray 5" meniscus type lens).

My puzzle is, that I just cant focus with the stereo lenses fitted...it is like the FL is too short, which makes me wonder why they are fitted in the first place...:confused:

[Steven Tribe]

But I only need a single objective with the sliding lens board. I know MW very well and have a number of Swift lenses and a Suter aplanat from them.

Now I have found a photo online from the back that shows the the fitting of the central septum - which will fit exactly into the recesses in my tailboard mono/stereo. The front part of the septume is in bad condition and bulges out.

The link is earlycameras.co.uk. Click under "Stand". The third camera in the second is like mine "prepared for stereo". The fourth camera in this row - called Stereoscopic by Hurman - has a good description of how this septum is built-up AND a second photo lower down which shows the open back and septum in position.

Tim, I think there must be some sort of tension or the septum will bulge to one side or the other. I have checked the light through my dummy run and found that a distance of about a 1cm ( my bellows has a slight taper) will still kept light away from the other section. My guess is that your two rings were for elastic/rubber - especialy if one is the the top and the other, near the bottom. Look for cutouts at the back.

[Chauncey Walden]

Steven, what I plan to do with my stereo tailboard is use 3 pieces of darkslide, one sliding inside the other 2. The two being attached to an upright for the rear slots and the single attached to the front. The square bellows allow this as do the pair of 135mm Tessars that I picked up from Surplus Shed for a few dollars some years back.

[Steven Tribe]

I have completed the "manufacture" of the central, removeable, septum. The making of the two struts was comparitively easy. Instead of planing down two pieces of mahogany to fit, I used a few few scrap pieces of walnut which is just as strong and workable. The bellows section is made using standard cut widths of plastic reinforced card with thin, slightly elastic, cloth on both sides. The two holes (3mm) were drilled through the whole assembly when glued to the two mounting struts. Attempts with commercial (dress shop accessories - knickers elastic?) elastic were not succesful as the diameter of the elastic prevented even expansion and compression of the bellows folds. I removed the outer material cover and found 10 1cmx1cm core rubber strands, which, grouped into 2 x5 rubber strands (glued at both ends) worked perfectly. The expansion is more than 3 times the length, whilst the "knickers" elastic could only manage around 2 times. This rubber will not last for ever - but is quite easy to renew at some stage. The range of dimensions I have now (lens board to GG) is 7.5 cm to 28cm - actually the full range of the camera without using the base extension camera. I enclose some photos. I have not trimmed the loose ends of the rubbers or of the outer edges of the bellows, so the construction is a little more understandable.