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C mount on a Bolex ... strength?


Jon O'Brien
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For years, with 16mm, I always wanted a Super 16 Bolex SBM, with the strong bayonet mount. I ended up getting a Rx-5, with the 3 lens turret. The fellow in Germany who sold it to me also supplied a Nikon lens mount to C mount adapter. This has actually turned out to be great, as my two 35mm cameras also have Nikon lens mounts. Anyone know how strong the C mount is on a Bolex lens turret? How heavy a lens can you fit on it. I'm thinking of buy some cheaper second hand Nikkors on ebay, maybe some zooms. The turret looks really thin and not all that inspiring in terms of robustness. What thinks thou? Okay to put some reasonably heavy zooms on a C mount long term without a, so to speak, sagging occurring?

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the problem with the Bolex turret is that it is only attached with one screw and it is hold at correct position with spring pressure. So adding a heavy lens will lift it off of its base and creates a gap between the turret and the camera body which of course messes up the FFD momentarily even if not breaking anything. Using the screw-on turret locking thingy one could use lenses like the Vario-Switar or similar size and weight. With heavy and long lenses it is mandatory to use additional support. Personally I use additional support with all lenses which are long barrel or heavier than about 1 or 1.5kg . When talking about stills lenses, most of the heavy and long ones are extreme telephoto or long zooms so they would need the additional support anyway to get a reasonable image out of them. It is pretty easy to modify a basic dslr-style 15mm rod support to work with the Bolex so additional support should be no problem (just use riser rod blocks to get the rods to the correct height) 

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Heavy optics are inconsistent with the concept of turret cameras. A turret provides you with a choice of two to six prime lenses. The classic amateur and semipro three-ports turret invites to have a normal focal length, a wide angle, and a tele. The idea is preparation for long, medium, and narrower shots, often done so by reporters.

With an older Paillard-Bolex H (as with many other upright cameras) you have a small base surface. Long or heavy lenses not only pull on the turret, a solved problem, they challenge the camera’s stability on the support. At least one of the two base plate models should be used (sheet alum, cast alum with compendium holder).

The C-mount thread is stronger than the turret plate. I have had bent turret plates for repair, after a camera got hit on a mounted lens.

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Thanks Simon and Aapo. Best solution is to stick with the little Switar 16mm I've got on it, and for telephoto just use some Nikkors. I need one more lens for the turret. I'd so much prefer a zoom on it. I grew up with zooms, with Super 😎 but ah well. That's life. Such a drag clicking that turret around ... life's tough sometimes ain't it. Just joking. One thing I'd really like to get is an electric motor for it. No words can describe the frustration and stress of trying to direct actors who want to crack jokes and engage the cinematographer/director in witty repartee while he's trying to change the turret, wind the mechanism, put the turret back again to the correct lens, take the reading ......

Edited by Jon O'Brien
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Hi Jon,

it's me, the guy who sold you your RX5 S-16 some years ago. Hopefully you are still happy with this camera.

If you use the locking screw in the free turret hole and the tiny fixing lever on top, a lens up to around 1,5 Kg should not be a problem.

I regularly use my  Vario-Switar 16-100 (1,4Kg) or Nikkor telelenses up to 300mm,  the old Ais  4,5/300 ED lens, with or without additional support. A good idea is to use the large Bolex compendium as support.

If you don't already have the turret locking screw, I could help you.

By the way, in 2010 I have been traveling with your Bolex and the above mentioned lenses in Western Australia, Murchison River, Shark bay and down south into the forests. Never been in the eastern states, except Tasmania. Love it  !!!

Let me know if you need the turret fixing screw, I could part with one.

All the best,

Volker

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Hi Volker,

I'm very happy with the camera, it's in excellent condition. You actually gave me one of those locking screw caps for the turret, along with the Nikon lens mount (thank you!).

Do you happen to know much about a good electric motor for this model - probably it will be a second hand motor from ebay. If I get an electric motor, I won't have to shift the turret to wind the mechanism.

If the turrent and C mount is strong enough for a small, lightweight Nikon zoom then really there's no need for me to think about changing to a camera with a stronger bayonet mount. I will have to do some research and see if there's an affordable Nikon zoom that can go wide enough for a reasonably medium lens for S16. How nice to know my camera has already been on some filming adventures in Australia!

Also, is it possible for you to post a photograph, or link to a site that shows the large Bolex compendium that you mention?

Best wishes,

Jon

Edited by Jon O'Brien
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Jon,

What kind of range are you looking for in a Nikkor zoom? The problem you're going to encounter is that all the 35mm camera constant aperture zooms (by any brand) are going to be heavy. The 17-35 f/2.8 is excellent and very large. Pretty dark for a reflex. The old AF-D 18-35 is very light but has a variable aperture f/3.5-5.6. The 20-35mm f/2.8 is one of the very best and the older brother of the 17-35, also heavy. The uncommon 25-50 is a little heavy but a constant f/4. Too dark for a reflex. You can't put G lenses on a C mount camera because you can't control the aperture, so you need older AF-D, AiS or Ai lenses. The 70-200 f/2.8 and 80-200 f/2.8 are very heavy, put a lot of torque on the lightweight mount and they are really dark for that focal length and weight. You should have any of these lenses I mentioned well supported. 

In a nutshell, you can have lightweight or constant aperture zooms in the NIkkor range, but not both. The fastest zoom you'll find that you have control over the aperture will be f/2.8. 

Once you decide on your lens, you're going to find that every one of them exhibits focus breathing. It doesn't bother still photographers. you may want to have your aperture rings serviced to take out the hard clicks.

Just a few things to think about.

Phil Forrest

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Hi Philip,

Thanks for all of your great points you raise. It sounds as though one of these 17-35 f/2.8 shouldn't be too heavy, if using the turret screw cap and locking device as outlined by Volker, above. He's done a lot of filming with some heavier Nikkors. The f/2.8 would have to be stopped down a bit anyway, on the reflex Bolex as these are designed for use with the special Rx lenses. Non-Rx lenses have to be stopped down generally to around f4 to get around the prism effect.

Because this is Australia, with lots of light, and I'm usually filming outdoors in sunlight, these lenses should be fine. So far the focus breathing hasn't irked me and it's possible I could pay someone to de-click the aperture rings. After all I hear there's rather a good lens tech available in my country but I don't know if he'd be interested in this work on the side 🙂

Then again, I wonder if I could get by without de-clicking the aperture rings. Would devalue the lens for resale.

Jon

Edited by Jon O'Brien
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By the way, with a 17-35 zoom on the turret, can anyone suggest a fine second prime lens to also go on turret? Something wider than the Switar 16mm I've got. Or maybe that's about as wide as you can practically go with S16 without spending a fortune. The good thing about the Switar is that it's a Rx lens, so if I need more light getting in I've got at least one lens there. For telephoto, I've got Nikkor primes if I need a longer focus lens than 35mm.

Edited by Jon O'Brien
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Jon,

For telecentric lenses, such as the 17-35, you shouldn't have to stop it down. The difference between RX lenses and those which are not is in the exit pupil of the lens. All 35mm SLR lenses will have an exit pupil far enough away from the prism so as to not be affected. The reason for this all is that the light rays are hitting the prism and film almost exactly perpendicular. This is the reason that lenses over 50mm were never corrected for this, as Bolex must have surmised that with long focus lenses, the light rays hitting the prism and film would be straight on. With shorter focal length lenses, the exit pupil is closer and the light rays hit at varying degrees, like a shallow cone. Digital rangefinders like the Leica M8 and M9 are plagued with this problem which causes a dramatic color shift around the edges with some wide angles. This is the reason Leica has moved to larger, longer telecentric lenses since the introduction of the generation of lenses after the M9. The exit pupil of any Nikon SLR lens on an adapter will be very far from the prism and so won't be a problem. You could use any Nikkor and it will work perfectly, with no softening of the image, regardless of the maximum aperture. 

To answer your recent wide angle question, the Switar 10mm RX, Cinegon  10mm, and Cine Navitar 12.5 are good lenses wider than 16mm.

Phil Forrest

 

 

Edited by Philip Forrest
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This is great news, Philip! Thanks for your extremely helpful input on this. My knowledge of filmmaking continues to grow, with such help. I will start researching lenses that are affordable.

For Australian readers: does anyone know if film development is still available here? I will check the Neglab website. Film scanning is available at Cameraquip, Melbourne.

Edited by Jon O'Brien
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  • 1 month later...

Hi Jon,

apologize for the delay, it took some time to make the photos.

This is to demonstrate the use of the Bolex Kompendium as a lens support.

And the attached small electric motor MC 17.

This is the smallest Bolex motor,  weighs 600 g only.

It's not quartz controlled, speed control goes with the frame dial of the camera.

It can also be used with different types of remote control.

Please let me know if you are interested, I have two of them and could part with one.

The Kompendium is also available.

Cheers,

Volker

 

 

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Just to chime in here; the official Bolex rails are sometimes hard to come by. I figured out how to rig normal lens support rods to a Bolex without using a cheese plate. The key was a Nato rail, attached to the Bolex with M6 metric screws. All cheap SmallRig components. The Nato rail I got was 7cm long, but I would go for a slightly longer one. 

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