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David Sekanina

Y8 camera: C-mount lenses, barrel diameter, flange protrusion

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Hi

 

For a camera project I don't want to exceed the dimension of the spinning mirror (and therefore the overall width of the camera body) so I ended up with a solution that accepts C-mount lenses with a barrel diameter of max 40mm (for the first 10mm from the mount forward) and can't have lens elements that protrude more than 8mm inwards into the camera.

 

Do many of your favorite Super8 lenses exceed these dimensions? I found a few zoom and wide angle lenses that would not fit, but a vast majority would.

 

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Yes, with Kodak breathing new life into the format I thought it might be fun to to develop a more silent one :)

 

The design looks nice! Reminds me of an Aaton and Eclair ACL :)

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Congratulations, David! Wonderful. Can you explain the design of the spinning mirror? Why the stepped pattern? I am intrigued by your other design the Super 8 prototype is sitting on. Were you exploring other mounts? PL? Is that a mockup of an over the shoulder co-axial mag? Are you designing a digital servo motor with firmware upgrades? What is the actual pull down mechanism? If I may ask...what is your background?

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I don't think so Heikki. Check out his amazing cad cam wire drawing form his other thread. It appears to have some sort of shoulder mounted magazine, i.e. http://www.cinematography.com/index.php?showtopic=73602#entry471303

 

Film camera wouldn't need a fan. Take a closer look at the magazine (this drawing is on the website), there are two HDDs and connectors: https://static1.squarespace.com/static/5555aec3e4b0849a888de601/5555b08de4b07b37133085ec/55c27b83e4b01d31318a16a2/1463744484977/y2_1.JPG?format=1000w

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@Nicholas

The spinning mirror is the same concept you'll find in all Arri and Aaton and many other film cameras - it's angled at 50 degrees, not at 45 to give me more room for the ground glass and the prisms above the mirror, like on the Aatons. The steps are there for the same reason you have steps inside lens hoods and lens barrels - it prevents light being reflected back creating ghost images because flat black anodized don't absorb all light. PL mount might be an overkill for this camera - although it would give me much less of a headache, because the FFD would be much bigger and I'd have more room for everything :)

 

The other camera (Y2) is an old project of a 2/3" digital cinema camera I worked on from 2006-2009...time flies - the Swiss company that developed the quadcore embedded platform that went into the camera was bought by a bigger competitor and the announced module I was waiting for got cancelled :/

It also had a spinning reflex mirror for the Aaton optical viewfinder.

 

The Y8 I'm working on right now (the black mock-up in the pic) will have a Maxon brushless servo - pull-down mechanism very similar to an Aaton. No register pin.

 

My background - I started as an industrial designer and now work as a senior mechanical engineer. I owned and serviced an Arri 16BL, SR3, Aaton LTR7. My father was an opto-electronics engineer and owned and repaired 16mm high-speed cameras, built big wooden cameras and collected camera curiosities from the former USSR - guess I caught his bug :)

 

Back to my question - you think I'd limit the camera too much with the lens dimensions I described?

 

EDIT: oh I forgot - I joined the forum as there are a few people who have a profound knowledge in Super8 cameras and I might ask them from time to time how much torque in mN the slip clutch on their cameras measure...things like that :)

Edited by David Sekanina
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PL mount would definitely be an overkill :) Wide angle lenses would be hard to come by. Sometimes I have been wondering if micro 4/3 mount would work on these small gauge cameras. Probably would work better in a 16mm film camera...

 

The only problem with the dimensions you mentioned is if one is using lens adapters such as Contax Yashica to C-mount. Other than that I think most of the super-8 c-mount lenses would work. I think I have to measure the dimensions of my Angenieux 6-80mm f1.2 though...

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Only two major manufacturers offered super8 cameras with C-mount: Beaulieu and Pathe.

Most often, the lenses made especially for these were either Angenieux or Schneider.

In my experience, in no case did the rear element housing extend more than 1mm into the flange.

Considering that the required area for the meter could be less than the standard Aaton or Eclair mirrors, there should be ample flexibility in positioning the rotating mirror.

 

Jean-Louis

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Heikki, I'll join as soon as I have a working prototype (no earlier than April) - till then it's just a silly project I spend oodles of time and money on because I truly enjoy it :lol:

Edited by David Sekanina

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Hi David,

Good luck with the design! So you're squeezing a mirror/ shutter in about a 9.5mm gap?

 

As Jean-Louis mentioned, the range of Super 8 cameras with a C mount was quite limited, and so the pool of C mount lenses specifically designed for Super 8 is also quite small. I think all of those lenses should be within your specifications.

 

A vaster selection of C mount lenses exists for 16mm, which in general should also be OK. Once 16mm turret cameras were developed in the late 20s, all C mounts needed to have a rear protrusion that was shallow enough to allow the turret to be rotated with lenses attached - meaning no greater than the thickness of the turret plate, about 4mm.

 

The problems arise with the advent of C mount TV lenses, and now machine vision lenses. These have no requirements in terms of rear protrusion and can sometimes extend back further than 8mm. In terms of potentially hitting a spinning mirror, this could be catastrophic, so it might be worth thinking of ways to block an incompatible lens (like Beaulieu using an aperture plate within the mount, just in front of their oscillating mirror). Though maybe just a specification measurement and boldly highlighted warning would be enough.

 

As far as I know, only one small format (under 16mm) camera was ever made with a spinning mirror/shutter: the rather awesome Pentaflex 8 manufactured in the former East Germany. It was a Standard 8 camera with loadable cartridges and its own custom Zeiss Jena lenses and breech mount. The flange depth was larger than C mount to accommodate the mirror.

 

Having worked on many spinning mirror cameras I can tell you that achieving a dead flat spinning surface in order to avoid any image jitter can be a tricky business.

 

All the best with your endeavours!

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David,


Again a wonderful initiative and thank you for interacting with us. Multiple perspectives are forthcoming and that just happens to be part of the equation once something as exciting as your project is released into the ether.


I have much to say about lens mount but I will say there is something to be said for the planar flatness of the PL standard which I suspect was modeled on the smaller robust Bolex breech mount with a 23.22 mm FDD. Eclair ACL has a fascinating interchangeable universal lens mount system that incorporates the venerable C-Mount, CA-1 (Eclair), Arri and Nikon lens mounts. Have you checked into P+S TECHNIK Interchangeable Mount System (IMS)? A German company staffed by ex-Arri engineers. These are the general specs and also a IMS 1.0 C-Mount adapter cameras with IMS interface, i.e.





I believe the C-Mount is absent royalty fees which may or may not be a factor in your intended price points but in my opinion it is a less than robust lens mount for heavier zooms and is prone to play. And as Don has indicated the C-Mount "spec" is somewhat variable. I don't think a C-Mount is necessarily a limitation but a more professional adaptable accurate lens mount system elevates your project to serious interest by industry heavyweights including active cinematographers.


Are your intentions to refine a working prototype such as to generate industry interest? The current level of global interest in motion picture film, formats and cameras is heartening and I suspect robust for the near future. In contrast the hardcore never dissipated. The DIY ingenuity exemplified by yourself and many others is inspiring.

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Hi David Sekanina,

Great project! I would suggest a PL version of the camera.
I am currently using a Pro8 Classic camera (ex-Beaulieu) with an adapter to be able to use PL lenses.
There is a great choice of cinema optics based on PL mount.

All the best,
Daniel Henríquez Ilic

post-2352-0-69927400-1485196385_thumb.jpg

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Hi Daniel - yes the PL mount would at least give the option to use some 16mm wide angle lenses. Alternatively I'm looking into the Leica M mount - but the widest non fisheye lens I found was a Voigtländer 10mm.

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Hi David,

 

The widest non fish eye lens I have used with that setup (camera + adapter) is a Carl Zeiss Ultra Prime 8R.

 

"The Ultra Prime 8R/T2.8 is an extreme wide angle lens with a unique look unparalleled by any other lens in the film or video world. Because of its rectilinear design it shows an extremely wide angle of view without any of the commonly associated fisheye distortions."

source : https://www.arri.com/es/camera/cine_lenses/prime_lenses/ultra_prime_8r/

 

In case it could be useful for your project, I do have an old PL to C mount adapter (that is deffective at the C mount side) that I am not using for a while. You may eventually use the PL mount of it (provided you can remove the C-mount, and transform the lens adapter in just a PL-mount). I would be happy to support your research by providing this item as long as shipping and duties are paid by your end.

 

All the best,

Daniel Henriquez Ilic

Fotoquimica Films SpA

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Hi Daniel

 

Very generous of you, but if I decide to go with a PL mount (that thing is huge on the tiny Y8 body :) ), I'd go with a hard front design like I did on the Y2 instead of mounting it onto the front camera housing. Cannibalizing your mount would be more of a hassle than me machining a new one to the dimensions needed to fit the hard front. But thank you.

 

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Edited by David Sekanina

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Such a great start! Reminds me just a little of the Arri 535 design...just the outside of course.

 

PL would be wonderful for professionals, but if your target is more hobbyists, I'd suggest Canon mount because of all the glass that's available these days in that mount. I love Nikon but their opposite focus direction can mess with some people.

 

There are many inexpensive C-Mount lenses available in the surveillance market, but they are not usually very good glass. The older c-mount lenses can be good, but most have aged poorly.

 

Is there a possibility of multiple mount options? Since lenses are such a major investment, having a PL, Canon & Nikon option these days might help you sell a few more...but perhaps too difficult to achieve.

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Yes these days given the cross-over between still, video and cine markets, interchangeable mount systems are what people often want.

 

There are some already out there - as Nicholas mentioned, Eclair's TS Intermediate mount as used on the ACL is able to adapt from the base C-mount to virtually any mount with a flange depth greater than 17.52mm. My Chrosziel Lens Test Projector uses the same system, it's very accurate and robust, and the original mount options are now much more varied. I've machined up several of my own.

 

There's also the P&S Technik IMS system that Nicholas mentioned.

 

Alternatively, you could use interchangeable front-end mounts, which is something RED and Arri use.

 

C-mount can adapt to various other mounts, but it's not really robust enough for heavy lenses, and it doesn't lock.

 

The problem with using something like a Canon (or M4/3) mount is finding wide angle lenses down to say 5 or 6mm, which is what you'd want for Super 8. There are a few 16mm PL lenses that can get to 6mm or below (some very pricey), but the best options really are in C-mount, like the Super 8 zooms that went down to 6mm, Century wide angles, C-mount versions of things like an Angenieux 5.9mm or Kinoptik 5.7mm, or maybe even some machine vision or CCTV C-mounts (as long as the rear protrusion is within the 8mm limit).

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Another camera would be fantastic!

 

I'd like to mention that I have several lenses from my Baulieus but none will fit a a camera with a front protrusion, like a front rotating mirror, due to the Beaulieu side tubes. They can be removed but the lens gears are then exposed, not ideal.

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