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Flange Focal Distance For BNCR Lenses

Published : 2nd Febraury 2007

Please confirm that the flange focal distance for BNCR lenses is 68mm. Thanks!

Greg Lowry
Scopica Inc. / Scopica 3D
Vancouver


My Richter standard states that the flange focal distance of a BNC Mitchell is 2.420 inches.


I mostly work on 16mm lenses, but I reckon Wikipedia is incorrect.

Ken Hale
Technician
Whitehouse Audio Visual
Southern California


Flange focal distance of a BNC Mitchell is 2.420 inches which equals 61.468mm

Quite close to the Russian OCT-19 mount which has a flange focal distance of 61mm (similar diameter too)

Cya

Steve Morton

Scientific Imaging
Monash University
Melbourne
Australia


Hi,

Mitchell BNC & BNCR (nominal) 2.420

Mitchell BNC & BNCR (recommended) 2.4188 Tolerance +/- 0.0001

For Photosonics BNCR mount 2.419 Tolerance 0.0005

Source: Samuelson's Hands on Manual

Hope this helps,

Emmanuel, Munich

Assistant Caméra - Camera Assistant - Kamera Assistent
BVK- European based
Mobil# Munich +491608036889 - London +447910034443 (please use German
number)
cml-listmum


Kenneth R. Hale wrote:

class="style15">>My Richter standard states that the flange focal distance of a BNC >Mitchell is 2.420 inches.

Hi, Ken:

I'm pretty sure BNC and BNCR are different.

Jeff "as are Mitchell standard and 2709 mounts" Kreines


Kenneth R. Hale wrote :

>My Richter standard states that the flange focal distance of a BNC >Mitchell is 2.420 inches.
>I mostly work on 16mm lenses, but I reckon Wikipedia is incorrect.

Thanks, Ken. It's not just Wikipedia that is incorrect. A variety of online sources have conflicting info, but it's identical conflicting info. Some claim that the flange focal depth is 2.420" (61.468mm).

Some claim that it's 68mm. I think it's a matter of the flange focal depth dimension being confused with the mount diameter dimension. The flange focal depth is, as you say, 61.468 mm. And the mount diameter is 68mm. (yes?) The problem with misinformation on the internet is that it is oft repeated until it can appears authoritative. It rarely is. That's why I asked the esteemed CML members for confirmation. My problem is that my ASC Manuals dating back to the 70s have gone missing. Grrrr!

What IS the best source for this kind of info?

Danke to Emmanuel in Munich and Steven Morton for confirmation that
it's 61.468mm.

Greg Lowry
Scopica Inc. / Scopica3D
Vancouver


One more vote for 2.42 inch!

2.420 inch nominal = 61.468mm (the inch standard is the master, so 61.47mm is plus two microns) and this would be the lens and ground glass setting.

For ARRI cameras with BNCR mounts the correct setting with tolerance is 61.45 to 61.46mm to the gate surface. I've only run into one person with a BNCR ARRI in seven years!

Now, does anyone have an authoritative standard for the OCT-19 mount?

Exactly 61.00mm?

And P.S. ARRI 65mm format Maxi-PL mount is 73.5mm... If anybody cares...

Jorge Diaz-Amador
Designer / Technician
CinemaTechnic, Inc.
Miami, FL USA
http://www.cinematechnic.com


Jorge Diaz-Amador wrote :

class="style15">> One more vote for 2.42 inch!

It's turning into a landslide victory for 2.42 inch. However, the verdict is still out about the lens mount diameter. Is it not 68mm?

Greg Lowry
Scopica Inc. / Scopica3D
Vancouver


Jorge wrote :

class="style15">>does anyone have an authoritative standard for the OCT-19 mount?
>Exactly 61.00mm?

My Russian Konvas 2M manual says 61.00 + 0.01mm

Have to dig out my Kinor 35H manual and see if it says the same...

Cya

Steve Morton

Scientific Imaging
Monash University
Melbourne
Australia


Greg Lowry wrote :

class="style15">>>However, the verdict is still out about the lens mount diameter. Is it not >>68mm?

Greg,

I have just measured 12 lenses I own. They vary between 68.18 and 68.22, 5 of which are 68.20mm or 2.685 inches.

I have a Fries Mitchell mount that is way oversize @ 68.25 the lenses are not tight. My callipers are too short to measure my Ultracam but I would guess 68.22 as that lens is a tight fit.

Stephen Williams DoP
Isle of Man, London, Geneva & Zurich in the last week.

www.stephenw.com


Stephen Williams wrote :

class="style15">> I have just measured 12 lenses I own.

You're very kind to do that, Stephen. Many thanks! I owe you a pint ... or two.

Greg Lowry
Scopica Inc. / Scopica3D
Vancouver


Kenneth R. Hale wrote :

class="style15">>>My Richter standard states that the flange focal distance of a BNC >>Mitchell is 2.420 inches.

Thanks, Ken. It's not just Wikipedia that is incorrect. A variety of online sources have conflicting info, but it's identical conflicting info. Some claim that the flange focal depth is 2.420" (61.468mm).

Some claim that it's 68mm. I think it's a matter of the flange focal depth dimension being confused with the mount diameter dimension. The flange focal depth is, as you say, 61.468 mm. And the mount diameter is 68mm. (yes?) The problem with misinformation on the internet is that it is oft repeated until it can appears authoritative. It rarely is. That's why I asked the esteemed cml members for confirmation.

My problem is that my ASC Manuals dating back to the 70s have gone missing. Grrrr!

What IS the best source for this kind of info?

Danke to Emmanuel in Munich and Steven Morton for confirmation that
it's 61.468mm.

Greg Lowry
Scopica Inc. / Scopica3D
Vancouver


class="style15">>>The problem with misinformation on the internet is that it is oft >>repeated until it can appears authoritative.
>> What IS the best source for this kind of info?

Hello Greg Lowry,

Truth by repetition, truth by cut and paste.

My '73 AC manual states 2.420 inches for the Mitchell BNC, 1.695 inches for the Mitchell NC, and 2.250 inches for the Mitchell S35R. Oddly, I see no mention of the BNCR camera. This forum seems to be the best place for this type of information, oh, and my scruffy tech-note riddled piece of paper that came directly from Cinema Products. Just looking at all the obscure camera flange distances....anyway, this piece of paper states that the BNC, and the BNCR are the same 2.420 distance, BUT that the BNCR w/beamsplitter is 2.4235 inches.

Cinema Products used to put beamsplitters into those cameras, and those should be 2.4235 inches, however any cameras with an actual mirrored shutter should be 2.420 inches. Please check to see what flavour of BNCR camera you have.

Ken Hale
Technician
Whitehouse Audio Visual
Southern California


Hello Jeff,

Thank you, it does seems that the cameras are indeed, different.

But the flange distances are the same for some, if not most, of them.

If you need any really, really obscure flange depths, please just ask, I have found my notes and I am ready to try and help.

Best regards,

Ken Hale
Technician
Whitehouse audio Visual
Southern California


Kenneth R. Hale wrote :

class="style15">>If you need any really, really obscure flange depths, please just ask, I >have found my notes and I am ready to try and help.

Ken Hale, the cml go-to guy for obscure flange depths. Keep those notes at the ready, Ken!

Greg Lowry
Scopica Inc. / Scopica3D
Vancouver


I have the First seven editions of the ASC manual, and I just found them from storage, what is it you are looking for?

Steven Gladstone
New York Based Cinematographer
Gladstone Films
www.gladstonefilms.com


Steven Gladstone wrote :

class="style15">>I have the First seven editions of the ASC manual, and I just found them >from storage, what is it you are looking for?

I managed to get the info I needed from a variety of helpful cml members. Keep those ASC manuals handy though. Thanks.

Greg Lowry
Scopica Inc. / Scopica3D
Vancouver



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