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Why are 15mm Studio Rods Offset from the Camera's Optical Center?


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#1 Karl Lee

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Posted 13 September 2014 - 11:57 PM

I recently bought an Arri BP-7 bridge plate to use with my SR3, and I was a little surprised when I noticed that the rods on the BP-7 are offset from the camera's optical center (compared to my 15mm lightweight rods which are perfectly centered).  I knew that the width between 15mm studio rods was wider than between 15mm lightweight rods, however I didn't realize until I did a little research that the studio rods are, by design, offset from the optical center by 17.25mm. 

 

Out of curiosity, does anyone know why the 15mm studio rod standard has a 17.25mm offset from the camera's optical center?  The 15mm lightweight and 19mm studio rods are perfectly centered, yet the 15mm studio rods have the 17.25mm offset.  On the surface, the offset seems kind of counter-intuitive, so I'd be interested to know why such an offset exists.

 

Also, in terms of studio rods, which format is more commonly used today - 15mm studio or 19mm studio?

 

In case anyone is interested, Arri has a nice chart which specifies the dimensions and offsets of the three rod variations. 

 

 


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#2 Brian Drysdale

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Posted 14 September 2014 - 02:11 AM

I'm not sure if anyone actaully knows the reason, but OConnor do have some information here on support rods. 

 

http://www.ocon.com/...ards-explained/

 

Edit I've  just noticed that your diagram comes from OConner, so you may have read this.


Edited by Brian Drysdale, 14 September 2014 - 02:13 AM.

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#3 Brian Drysdale

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Posted 14 September 2014 - 02:35 AM

Another article, both seem to suggest the same reason for the off set.:

 

http://matthewduclos...le-explanation/

 

Everyone seems to use the same chart.


Edited by Brian Drysdale, 14 September 2014 - 02:37 AM.

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#4 Satsuki Murashige

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Posted 14 September 2014 - 12:06 PM

35mm film cameras of that era like the Panaflex and Arri BL (and even models used today) had their camera motor on the dumb side (left side when facing the lens) which created extra weight. So to balance out the load on the tripod head, the rods were offset.
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#5 Dom Jaeger

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Posted 14 September 2014 - 09:56 PM

I believe the 15mm studio rod standard was introduced by Arri in the 70s for the 35BL. (I can't see Panavision having anything to do with a metric standard, and before that Mitchell had their own 5/8 and 3/4 inch rod systems.)

 

Since the 35BL was designed to be a hand-held as well as studio camera, I'd say the rods were offset to better balance the camera for hand-held work. The rods are more or less centered around the camera mounting screw, which is aligned with the camera's centre of gravity. 


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#6 Kar Wai Ng

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Posted 14 September 2014 - 10:10 PM

I second Satsuki's explanation. It was always my understanding that the offset was designed during the BL era to balance out the weight of the motor. 


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#7 Gregory Irwin

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Posted 14 September 2014 - 10:24 PM

Could it be set for Super 35 vs. Standard 35 or the other way around?

Greg
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#8 Dom Jaeger

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Posted 14 September 2014 - 11:19 PM

Could it be set for Super 35 vs. Standard 35 or the other way around?

Greg

 

The difference between Super and Standard is only about 1.5mm, not much compared to the 17.25mm offset of the 15mm Studio rods.


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#9 Brian Drysdale

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Posted 15 September 2014 - 01:48 AM

I believe the 15mm studio rod standard was introduced by Arri in the 70s for the 35BL. (I can't see Panavision having anything to do with a metric standard, and before that Mitchell had their own 5/8 and 3/4 inch rod systems.)

 

 

Panavision went for an entirely different arrangement, with the support rods being vertical, on the motor side of the camera. As seen here:

 

http://upload.wikime...on_car_grip.jpg


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#10 Dom Jaeger

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Posted 15 September 2014 - 03:08 AM

Panavision went for an entirely different arrangement, with the support rods being vertical, on the motor side of the camera.

 

A design they borrowed from the Mitchell BNCR?

 

Mitchelrails_zpse86f271a.jpg


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#11 Satsuki Murashige

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Posted 15 September 2014 - 03:22 AM

Right, I totally spaced out about the Panavision rods system! I believe either Jon Fauer or Doug Hart explained about the rods offsetting the motor's weight in one of their books.

Btw, I think it's funny that the Sony F65 aped the 35mm camera look so much that it has the same "motor bulge" on the dumb side. Been shooting with it for the last two days and the Studio 15 rod offset does indeed keep the camera balanced for handheld.
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#12 Brian Drysdale

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Posted 15 September 2014 - 03:23 AM

Could be, since the PSR is a Mitchell underneath and so carried it over onto the Panaflex, since Panavision was about their lenses.


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#13 Gregory Irwin

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Posted 15 September 2014 - 06:50 PM

The difference between Super and Standard is only about 1.5mm, not much compared to the 17.25mm offset of the 15mm Studio rods.


Crap! I thought I was onto something good! :)
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