Conversion of a Bolex D8L to DS8
The Bolex wind-up cameras are not legendary for nothing. Especially with the excellent prime lenses of their time, they are simply very good, practical cameras. However, since the H8 is often simply too heavy and unwieldy, its little sisters (L8, B8, D8, D8L and D8LA) are very popular. They also have a turret, excellent film guidance and all imaginable extras and comfort features. A disadvantage, however, is that these cameras are all “only” intended for double-8 film. While the big sister H8 was converted to DS8 by at least four different technicians (Muster, Grebenstein, Pitterling, Jaakko Kurhi), such a conversion is very rare with the small D8 models. I’m only aware of one model of a converted D8, so the conversion is basically possible – and that’s why I’ve now tried it successfully!
It should be said in advance that the conversion was by no means easy. I spent a few weekends and evenings on it, had to start from scratch several times, kept looking for new solutions, experienced setbacks again and again – but in the end I managed it, and to my complete satisfaction. At least the quality of the conversion is at least as good as that of the only other conversion I know of, which film friend Uwe kindly lent me, to measure. Thank you, Uwe!
I hope these “instructions” can encourage other builders and reduce the many possible wrong turns. It’s not a step-by-step guide for the hasty hobbyist though. With patience, perseverance and the best possible tools, you can definitely achieve your goal. Patience is probably the most important requirement.
Tools and materials
I highly recommend organizing at least one (preferably two) Bolex bodies as part donors. Their condition doesn’t matter. There’s just nothing more annoying than being held up by a single spring or screw that has blown off. In addition, two mediocre cameras can often be made into one excellent one, and we do want to create an excellent DS8 camera after all!
You need the best possible tools. I have the “hardware store phase” behind me and have now invested in very fine tools and have never regretted this step. Of course, most things can also be done with simple equipment, but I still strongly recommend not skimping on tools. As the saying goes: Good tools are half the work, and if you buy cheap, you buy twice!
I found essential tools:
- Good needle files (for me: an assortment of “PFERD Corradi 266/16 Cut 2” files). The most important is the beret file.
- Good slotted screwdrivers (Wiha, Wera, or my favorite: Bergeon)
- A top-view stereo microscope (mine is old, has 20x magnification, but works really well with LED light)
- A magnifying glass or measuring loupe for precise film window magnification (0.05 mm precision preferred), or calipers if necessary, or both
- A watchmaker’s anvil and watchmaker’s hammer
- A gas stove or other “miniature forge” that gets steel glowing orange-red
- A Dremel with grinding pin (corundum)
- Polishing tips (felt) and polishing paste (coarse and fine, I use the brown one from Dremel and “Flitz” from Nettoyant for a high shine… brilliant stuff!)
- A small pillar drill is very helpful, of course with good drill bits
- A few rolls of expired DS8 test film (Kodak, Orwo, Wittner; Foma if necessary, but definitely not Kahl). You actually need more than one roll, since scratch tests naturally only go once.
- A 7.5m roll of DS8 film for test exposures (I took K25 and developed it into a negative)
- Any SW developer and fixer (no tank needed, we only make short test strips)
How to
Several steps are necessary for the conversion:
- Modification of the pressure plate
- Lengthening and widening of the claw slot
- Filing the gate
- Extension of the segment radii of the circular shutter
- Reshaping of the claw
- fine tuning and adjustment
The steps vary in difficulty, luckily the easy steps are a good place to start.
But first of all, as a kind of step 0, you should absolutely completely overhaul the camera to be converted. Not only so that it runs well and you can fix any defects, but above all to get to know the camera well. There is a pretty good guide on how to do this here, I don’t recommend skipping a single step, even be a little more thorough. It’s worth the effort and you get to know the camera well. Some parts and assemblies will have to be dismantled and reassembled umpteen times during the conversion, so it helps if everything is done correctly.
1. Modification of the pressure plate
This step is easy. Use a round file to widen the cut-out for the claw tip in the pressure plate. I lengthened the long hole in the carrier plate from 9.5 mm to 10.9 mm towards the middle. The cut on the actual pressure plate is then extended accordingly, approx. 1 mm is enough – here you can work on sight (view through). It is important here to round and polish the edges afterwards. The pressure plate itself should remain nice and black and should not be polished.
Incidentally, it is already worthwhile to pay meticulous attention to the fact that not a bit of sanding dust or burrs end up in the camera. A virtually invisible metal splint in the half-open ball bearing of the shutter can drive you crazy for a whole night, I speak from experience….
2. Lengthening and widening of the claw slot
For this step, we first remove the camera head and loosen the film path incl. of the drive block. I recommend taping the shim of the insane trigger mechanism on three sides so you don’t have to keep replanting all those flat levers and springs. But after about the third time “Tetris” you know how to successfully avoid self-disassembly of this Swiss “masterpiece”…
On the film path, the claw slot is now first extended in the direction of the gate . I drilled a hole here with a 1.5 mm HSS drill and only filed the transition:
It was quick and turned out nicely. However, the claw slot is now a bit too long, when using longer focal lengths with a large image circle, backlighting can lead to “ghost images” at the bottom left, since the light falls on the next film frame before it is exposed. Maybe at some point I’ll make the slot smaller again. So I recommend filing here as well.
In the second step, use a file to widen the claw slot in the direction of the outer edge until the remaining metal is around 0.6 mm. The whole thing is quite good practice for handling the file: For a clean, straight and right-angled result, it is better to make a lot of light strokes than to try to remove a lot with a lot of force. Here you slowly get a feeling for the material of the film path.
The edges should then be broken (or slightly chamfered) and polished. Attention: Don’t polish too much on the surfaces with film contact, so that they stay flat! I first leveled the burr visible under the microscope with a probe (dentist).
Filing the gate
This step requires very careful work, because what’s gone is gone! Two things are particularly important when handling the file:
- The film path has different thicknesses, and material in the thinner areas wears away correspondingly faster. There is a risk of going wrong here.
- It is better to leave a little more material on the long (horizontal) edges than too little. This way you still have room to correct the edges of the gate that have accidentally become slightly crooked. A further widening is always possible later, a reduction not! An unexposed image line must be preserved, otherwise the sky will shine into the lower edge of the next image!
It is worthwhile to work absolutely meticulously, slowly and consistently as precisely as possible. Under no circumstances should great pressure be exerted on the file. The best way to check progress is with a microscope and/or magnifying glass. I even file all the way under the microscope, because the work looks appropriately brutal when enlarged accordingly, so that you automatically hold back more instead of getting impatient.
The measurement of the Super 8 film linked in the graphic is very helpful as a working basis. It is derived directly from the SMPTE Standard S149-2004. Attention. There are numerous incorrect measurements and specifications circulating on the Internet – absolutely ignore them! You should print out the PDF and have it ready.
The only edge of the film window that does not need to be altered is the narrow edge of the image opposite the perforation hole. With double 8, this is already closer to the edge of the film than with Super 8 — whether we like it or not, our conversion will therefore be a “Max 8” conversion.
The following procedure has proven itself, whereby I mainly worked with the beret file, which is only milled on one surface and thus ensures the most precise corners:
- Expanding the gate by 1.1 mm in the direction of the perforation
- Expanding the gate by 0.27 mm upwards
- Widen the gate by 0.27 mm downwards
The result should be no more than 4.22mm image height, but will be wider than the 5.69mm specification (see above). A helpful mark is that the edge of the image facing the perforation hole almost reaches it.
At the very end, the gate will get a final treatment, more about that in section 6.
4. Extension of the shutter’s sector radii
Unfortunately, the radius (not the angle!) of the light sector is a bit tight on the small Bolex and would shadow the Super 8 image. We need to increase the radius with the Dremel, but fortunately there is enough “meat” on the shutter here. The biggest difficulty is to get the smooth adjustability of the variable shutter. Burr is to be removed painstakingly, the plates must not bend to the side when sanding. After expanding the radius (not the sector angle!), the shutter should be completely cleaned and re-lubricated to remove metal chips and the like from the gears and the tiny ball bearing.
For the time being, we are now reinstalling the shutter and film path in the camera in such a way that the gate can be seen as centered as possible from the front through the turret, at least on the short edge (i.e. in height when the camera is upright):
5. Forming of the claw
This step is the most difficult — or let’s say, the most time-consuming. I worked on my first claw for three weekends before it finally worked satisfactorily. Then, on a final correction, the tip broke off and I was deeply frustrated. Fortunately, the frustration only lasted for one day, because the time investment was worth it! Now that I knew what was important and how to proceed, the second claw was ready after just four hours — and it turned out much nicer and more precise than the first. So it was worth it — and thanks to the donor Bolex!
The claw needs to be changed in three parameters:
- Its tip must be offset by about half a perforation distance in the direction of the gate
- It must dip into the perforation hole closer to the edge of the film
- It needs to be narrower and flatter, at least at the tip
This is exactly the order in which we proceed. But before we move the claw tip, it is worth measuring how far we have to move it. The following applies here: measuring is better than calculating, because the ideal position of the claw tip depends directly on the position of the gate, and this is slightly variable. The aim is, of course, for the perforation hole to be as centered as possible next to the film image.
I fixed a piece of DS8 blank film (Kodak, fresh) on the film path in such a way that a perf hole is centered horizontally under the gate. In this position, the filmstrip should be temporarily secured with a piece of tape. Using tweezers and short pieces of tape, I have now marked where the left edges of the two perforation holes to the left are. This makes it easy to see where the claw has to enter and where it has to leave the perforation hole. It’s not (yet) a matter of hundredths of mm of accuracy, but without such markings you simply have no reference point as to how far the new claw actually has to be formed.
There is only one way to move the claw tip accordingly without making the claw shorter: forging. The claw must be fixed to a holding device so that it can be heated up to orange embers. This is the only way it can be reshaped with a hammer on a small anvil with a lot of patience.
The M3 screw, which “bolsters the claw ‘s back” in my holder, has proven to be very useful: it absorbs the forces that occur when the claw tip is driven to the right. The claw must not become an S-shape as a result of the reworking, otherwise it will be too short overall. Since the claw tip with its low mass cools down very quickly, a lot of patience is required. Most of the time it is no longer visibly glowing after just one or two strokes with the hammer. The only thing that helps here is constantly going back and forth between forge and anvil — and hammering carefully, because nobody wants dents and nicks. It’s hard to believe, but it actually does transform! In between you should check again and again whether you have already formed far enough. To do this, the claw must be allowed to cool down thoroughly. Under no circumstances should it be dipped in water or oil to cool it down, as that would harden it, and we (still) need it to be as soft as possible!
It is also important that the front tip of the claw remains as right angled as possible. As the thinnest part, it is the hottest and therefore also the softest. If necessary, it can be easily bent back into position (when heated to orange) with smooth flat-nosed pliers. Attention: The claw should never become yellow-hot, because then it loses substance and will sooner or later break. Glowing orange-red, it can be done dozens of times without taking damage.
If the lateral offset finally matches the markings made under the film path, the biggest step has been taken. the reshaping in the direction of the edge of the film, on the other hand, is easy. It is important not to bend the claw tip once, but rather to bend it at two points, because it has to enter the perforation hole largely perpendicular to the film.
The best way to see whether the offset is roughly correct is under a microscope. To do this, you switch the camera to the slowest gear in which it is still transporting (below 12 fps), activate the single image mode and you can now clearly see under the microscope (possibly further slowed down by additional braking of the helical gear wheel) where the claw will reach the sprocket. Small changes are also allowed here by careful cold forming.
If the shape fits by and large, the claw tip still needs to be filed flat. As can be seen below, it makes sense to halve the thickness, because the Super 8 specification allows for position tolerances of the perf hole . Also, we don’t want to destroy the rounded corners of the perforation. However, it must not be too narrow either, so that the hole edges do not suffer or the claw even bends.
Attention: The claw should not be shortened! The shape of the foremost tip is also important. The switching step of the D8 is only just enough for Super 8, which is why you have to work twice as precisely.
To polish the claw tip to a high gloss, I recommend a two-step procedure, first with a somewhat coarser and then with a very fine polishing paste. The smoother the claw tip, the quieter the camera, the more securely the film is transported and the less the film suffers!
6. Fine tuning and adjustment
The final step is the finishing touches.
After an initial assembly of the camera, a scratch test is recommended. Whiteboard marker applied to test film shows very clearly where the claw attaches and where the film would potentially be scratched.
With fresh film, any scratches can also be seen very well under the microscope. This works especially well with developed film — old Kodachrome can be developed into a negative and fixed within 5 minutes and is well suited for such scratch tests.
What is easily overlooked: the small Bolex cameras have two leaf springs in the lid, which provide lateral film pressure when the camera is closed. The pressure plate is also held in position by the lid. Whether the camera is transporting properly can only be judged with the lid closed, which is very impractical. To (roughly) assess the claw geometry, the film must therefore always be pressed down so that it rests on the two “cheeks”.
So that the film really does not get any scratches, not even superficial specks, I rounded off those changed parts of the film path that come into contact with the emulsion again and brought them to a high gloss with a felt cone and polishing paste.
A disadvantage of highly polished edges is that they reflect. This is annoying on the inner edges of the gate , which is why they are usually blackened. Without this blackening, “glowing” image edges easily occur. In order to blacken these inner edges, I taped the film window cleanly from the film side and sprayed on several thin layers of matt black enamel paint from the back, let it dry and baked it in the oven at 50°.
After the varnish has dried (I also re-laid the film side of the film path black, as parts of the original blackening suffered during polishing, see above), the camera can finally be fully reassembled. This time you have to be particularly careful, because further disassembly should not and will not be necessary in the near future.
In order to minimize vignetting and to center the lens image circle as well as possible over the newly formed image window, the film path must be positioned as close to the edge of the body as possible. The fixing pin and three screws holding the film track offer a little wiggle room here.
The rest of the drive block must also be aligned upwards and ideally lie directly against the film path. It must be ensured that the shutter (with the release button pressed) is able to move easily. Even scraping noises should not be heard. If in doubt, loosen parts of the block again and tighten carefully in a criss-cross pattern, without neglecting alignment with the edge of the housing.
During my first complete, exposed test rolls, I noticed that the closed camera sometimes started to “tick”, the image steadiness then became terrible and some frames were exposed twice. The reason for this are the two leaf springs in the lid, which have to be adjusted to the slightly offset film path, otherwise their pressure is simply too strong and they literally clamp the film.
To test the lateral pressure, I used an old Orwo UP21, whose carrier is particularly soft and thin (0.12 mm). Now the film is no longer jammed at the side and the image steadiness is very good from the first to the last image.
Unfortunately, the D8 doesn’t have a film transport gear, but what camera has everything you wish… I’m completely satisfied now, and as soon as the weather improves again, something real will be filmed!
Vignetting
Unfortunately, the image circle of the Kern lenses with a focal length of 5.5 mm is far too small for Super 8. Both the Switar and the Fix-Focus Pizar produce a semicircular vignette on the left edge of the image, which is very annoying. Due to the design, it is not possible to move the turret. However, switching to a Schneider Cinegon with 5.5/1.8 can help here, as its image circle is larger. It’s also at least as sharp, if not sharper, than the Kern lens. The top row of images in the image above (street scene) is filmed with the Schneider 5.5mm. Although there is still a small shading in the top left corner, it hardly disturbs the projected result.
Have fun imitating it — and don’t give up, it’s worth it!
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