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Mitchell BNC Mounts vs. BNCR


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Hi everyone – long time reader, first time poster!

I'm considering purchasing an Angenieux 18.5mm Type R2, and was previously under the assumption that the mount was Mitchell BNCR. The lens' owner, however, has just informed me it's not a BNCR mount but BNC. Apparently, these mounts are slightly different. As I don't know my way around a Mitchell (or anything Mitchell, for that matter), and as I've not got the budget to rehouse the lens, I'm wondering whether a BNC lens (in particular this Angenieux) would fit an EF to BNCR mount adapter.

I've been unable to source an EF to BNC adapter, so if I'm out of luck with the BNCR adapter I'm wondering if there might be other solutions to the problem.

Happy New Year,

Christian

 

 

 

 

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My understanding is that they are more or less the same in terms of the back-focus and diameter, but BNC mount lenses can protrude further back, and have a straight cylindrical rear protrusion rather than a tapered or bevelled one. Some BNCR adapters/lens mounts won't accept BNC mount lenses for this reason.

But Angenieux wide angle lenses were retro-focus designs which allowed for a deeper flange depth, so it shouldn't protrude back as far as earlier wide angle lenses did. You would need to check how far the Angenieux rear extends, and whether the adapter has enough clearance. Ask the seller for photos and dimensions of the rear protrusion.

If you're interested in the history, the BNC mount was the first locking mount designed for Mitchell cameras to allow lenses to be quickly interchanged. It was introduced with their Blimped News Camera (BNC) in 1934. Before that, they used a 4 lens turret with the lens mounts screwed on. In the 60's Mitchell cameras were converted to reflex viewing with a pellicle or spinning mirror, and so the clearance dimensions behind the mount had to be reduced. The R in BNCR stands for 'reflex'. The mount is a positive locking type, with 4 flanged wings - the direct antecedent of modern PL and PV mounts.

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15 hours ago, Dom Jaeger said:

My understanding is that they are more or less the same in terms of the back-focus and diameter, but BNC mount lenses can protrude further back, and have a straight cylindrical rear protrusion rather than a tapered or bevelled one. Some BNCR adapters/lens mounts won't accept BNC mount lenses for this reason.

But Angenieux wide angle lenses were retro-focus designs which allowed for a deeper flange depth, so it shouldn't protrude back as far as earlier wide angle lenses did. You would need to check how far the Angenieux rear extends, and whether the adapter has enough clearance. Ask the seller for photos and dimensions of the rear protrusion.

Dom, you are a godsend! And thanks for the history lesson – I needed it!

Angenieux introduced the 18.5mm in (I believe) 1951. I've read that the lens wouldn't cover the full frame sensor of (say) my 5D were I to adapt it, and that it'd be much like equipping an APS-C lens.

Any idea if this is true? If the lens was manufactured for a Mitchell camera, for Academy ratio, how could it be the case that the vignetting would be as severe as with an APS-C lens on a full frame camera?

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2 hours ago, Christian Flemm said:

Dom, you are a godsend! And thanks for the history lesson – I needed it!

Angenieux introduced the 18.5mm in (I believe) 1951. I've read that the lens wouldn't cover the full frame sensor of (say) my 5D were I to adapt it, and that it'd be much like equipping an APS-C lens.

Any idea if this is true? If the lens was manufactured for a Mitchell camera, for Academy ratio, how could it be the case that the vignetting would be as severe as with an APS-C lens on a full frame camera?

As David has explained, Academy is a much smaller frame than full frame stills, closer to APS-C. Because wide angle lenses are difficult to design, they almost always only just cover the format they were made for, so the Angenieux 18.5mm would definitely vignette on a full frame sensor.

The reason cine 35mm is smaller than stills 35mm is another interesting slice of history. 35mm film was originally only a moving picture medium, and moved vertically through the camera. So the rectangular frame had its long edge across the width of the film. Around 1913 an engineer by the name of Oskar Barnack who worked for the German optical firm of Leitz was working on a new cine camera when he made a small device to test the exposure speed of the 35mm film he was using. He designed it so the film moved horizontally across, so the rectangular frame used the film width as the short edge, roughly doubling the frame size. The device ended up being turned into a camera for still photography - the first Leica - and gave birth to what was then described as a “miniature” film format: 35mm still photography.


C7E39CAD-6105-4E00-96D0-214D18B7184E.thumb.jpeg.f42ab7d6dbe131534e5b230b78469bfc.jpeg

 

That Angenieux 18.5mm lens is also something of a historical landmark. When it was introduced in 1951, it was the widest 35mm format cine lens available. Many of Orson Welles’ movies from the 50s, including the classic Touch of Evil, were shot almost entirely with this lens.

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You also run into 4-perf 35mm still cameras which were called “half-frame” - the film ran horizontally so the stills were portrait mode (vertical) unless you rotated the camera 90 degrees. I played with a 35mm f2.7 Univex lens on my Nikon full-frame recently.

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  • 5 months later...
On 1/5/2021 at 9:25 PM, Christian Flemm said:

Dom, you are a godsend! And thanks for the history lesson – I needed it!

Angenieux introduced the 18.5mm in (I believe) 1951. I've read that the lens wouldn't cover the full frame sensor of (say) my 5D were I to adapt it, and that it'd be much like equipping an APS-C lens.

Any idea if this is true? If the lens was manufactured for a Mitchell camera, for Academy ratio, how could it be the case that the vignetting would be as severe as with an APS-C lens on a full frame camera?

Are you still looking at these lenses? I have three Angenieux 18.5mm which I've mounted on a variety of cameras.

On MFT there image circle covers perfectly (obviously), on modern S35 sensor there can be a touch of a vignetting in the corners. This depends on which version of the lens us used. The classic type as used on Touch of Evil has pretty clean coverage due to the wide built in lens hood.

On FF / 135, the image circle no where near covers.

Edited by Daniel J. Fox
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  • 2 weeks later...
On 6/21/2021 at 10:43 AM, Daniel J. Fox said:

 The classic type as used on Touch of Evil has pretty clean coverage due to the wide built in lens hood.

Bear in mind "Touch of Evil" was shot in regular 4-perf 35mm, which has a diagonal of (aprox) 27.2mm, while 4-perf Super 35mm is 31.1mm, thus increasing the risk of vignetting and/or portholing. Most of the modern S35 sized sensors at least 27mm or more.

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On 6/30/2021 at 9:39 PM, Ignacio Aguilar said:

Bear in mind "Touch of Evil" was shot in regular 4-perf 35mm, which has a diagonal of (aprox) 27.2mm, while 4-perf Super 35mm is 31.1mm, thus increasing the risk of vignetting and/or portholing. Most of the modern S35 sized sensors at least 27mm or more.

As I said, "pretty clean" coverage. ?

There is some darkening in the corners on S35, and clearly the illumination circle is being used to cover a modern S35 frame.

I'm still intending to have one of my lenses rehoused by Zero Optik and it will be interesting to see its coverage then, given the rehousings much wider frontage. I suspect the coverage will still be "tight", but acceptable and still better than the Cooke Speed Panchro 18mm.

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  • 1 month later...
On 6/21/2021 at 4:43 AM, Daniel J. Fox said:

Are you still looking at these lenses? I have three Angenieux 18.5mm which I've mounted on a variety of cameras.

On MFT there image circle covers perfectly (obviously), on modern S35 sensor there can be a touch of a vignetting in the corners. This depends on which version of the lens us used. The classic type as used on Touch of Evil has pretty clean coverage due to the wide built in lens hood.

On FF / 135, the image circle no where near covers.

Hey Daniel!

Sorry to have left you hanging. Indeed I've been looking at the 18.5mm lens quite a bit as of late, 'specially since I can't seem to adapt the one I bought ?

Dom noted that, prior to my purchase, due to the retrofocus architecture, attempting to adapt the 18.5mm BNC mount lens using a BNC-R to MFT/EF might prove difficult (due to it having a "straight cylindrical rear protrusion rather than a tapered or bevelled one"). So I wrote to the buyer who provided measurements of the rear element that seemed to put me in the clear; however, upon receiving the lens I discovered that the rear element was too large to fit through the back of the adapter (which, to a certain point, is bevelled - this beveling being the chief obstacle).

Given that you've adapted several of these lenses, I wonder if you might be able to offer up a BNC to MFT solution for the 18.5mm lens? I'd love nothing more than to adapt it, and I'm sure I'd have a hard time selling it with that mount. Geoffrey Berliner at the Penumbra Foundation suggested I find a Mitchell that's been torn apart and ask that the mount be drilled out so that I could machine my own adapter...sounds nice but highly unlikely! It should go without saying that the Zero Optik rehousing, while ideal, is absolutely out of my price range.

Here's to hoping that something'll come of this...

Best,

C

 

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On 8/25/2021 at 7:08 AM, Christian Flemm said:

Hey Daniel!

Sorry to have left you hanging. Indeed I've been looking at the 18.5mm lens quite a bit as of late, 'specially since I can't seem to adapt the one I bought ?

Dom noted that, prior to my purchase, due to the retrofocus architecture, attempting to adapt the 18.5mm BNC mount lens using a BNC-R to MFT/EF might prove difficult (due to it having a "straight cylindrical rear protrusion rather than a tapered or bevelled one"). So I wrote to the buyer who provided measurements of the rear element that seemed to put me in the clear; however, upon receiving the lens I discovered that the rear element was too large to fit through the back of the adapter (which, to a certain point, is bevelled - this beveling being the chief obstacle).

Given that you've adapted several of these lenses, I wonder if you might be able to offer up a BNC to MFT solution for the 18.5mm lens? I'd love nothing more than to adapt it, and I'm sure I'd have a hard time selling it with that mount. Geoffrey Berliner at the Penumbra Foundation suggested I find a Mitchell that's been torn apart and ask that the mount be drilled out so that I could machine my own adapter...sounds nice but highly unlikely! It should go without saying that the Zero Optik rehousing, while ideal, is absolutely out of my price range.

Here's to hoping that something'll come of this...

Best,

C

 

All of the lenses I've owned have been on Cameflex mount, which makes them very simple to adapt to MFT or any mirrorless mount. The Hawk's Factory adapters are by far the best, letting me use these lenses on both MFT and E-mount cameras.

So no, sorry no idea about adapting BNC. There are adapters out there that claim to be compatible, but it seems to be very much on a lens by lens basis.

https://www.ebay.co.uk/itm/133829143926?hash=item1f28d6ad76:g:KUoAAOSw4NFgL8-K

If a full rehousing by Zero Optik is beyond your budget, maybe enquire with Optitek...

http://optitek.org

... and see if they could rework just the mount for you. These Angenieux wide angles are really special. I have the 14.5mm as well and they are seeing increasing use on a variety of projects.

DSC00052.jpg

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