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As cameras get smaller


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#1 Katerina Diakoyanni

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Posted 10 January 2014 - 07:42 AM

Dear Operators,

 

I tried on two different setups yesterday. The first one was an Alexa and Zeiss Standard Speeds T2.1 lenses. The CG was 4 inches BEHIND the sensor of the camera.

 

The second setup was a Red Epic and Hawk anamorphics. The CG was now more than 4 inches FORWARD from the sensor. Although length-wise and weight-wise the two setups where pretty similar, on the second case, it was the lens that was sitting on top of the post and not the camera. Panning felt completely different, tilting felt completely different, as if more finesse was required.

 

At the moment, I didn’t think much of it, but later I realized that as cameras are getting constantly smaller and lighter, they will keep moving further and further behind the gimbal.

 

It is not a problem per se, but I was wondering if you guys have felt the difference in panning and tilting with the lens sitting on top of the post instead of the camera.

 

Katerina


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#2 Juan Lima

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Posted 10 January 2014 - 12:53 PM

Yes. Keep in mind Inertial balance. Relative angular inertia in all three axes.
Till axis is more inert than roll, less inert axis is pan.
Longer camera body (lens or not) increases angular inertia in the pan axis. Lower body reduce tilt inertia. Moving masses change the way you feel the sled. Think in what happens when you add extra masses to increase inertia and reduce rotation (Antlers, Gyros). The same principles apply here.
Big rigs with more mass have more inertia than smaller rigs. Smaller cameras, lower bodies and different inertial balance changes the way you "feel" and the way you operates the sled. ;)


Edited by Juan Lima, 10 January 2014 - 12:56 PM.

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#3 Chris Van Campen

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Posted 10 January 2014 - 01:22 PM

I would think that the closer the lens' nodal point is to being directly above the post / gimbal, the easier and more natural panning and tilting are going to behave.

 

I set my practice camera up this way on purpose.

 

So I would think having CG in front of the camera body is actually a good thing...


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#4 Juan Lima

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Posted 10 January 2014 - 06:56 PM

No matter lens, Camera or Matte Box. Once you put all together is a mass with a CG.

Eg If monitor is above battery CG, Camera CG is allways behind center post for Dinamic Balance. Usually 3/4 inch behind center post for bigger rigs.

Why did you take Lens Nodal Point as a reference?


Edited by Juan Lima, 10 January 2014 - 07:02 PM.

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#5 Eric Fletcher S.O.C.

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Posted 10 January 2014 - 07:15 PM

Eg If monitor is above battery CG, Camera CG is allways behind center post for Dinamic Balance. Usually 3/4 inch behind center post for bigger rigs.
Why did you take Lens Nodal Point as a reference?


Thats a pretty huge generalization. And often not true.

Nodal is good because when doing shots with stong veticals your tilt is exactly that a tilt. Not a arc
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#6 Victor Lazaro

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Posted 10 January 2014 - 08:15 PM

I don't like having the camera like Epic too far back. What I got used to to is place a battery at the back of it and try to place all accessories toward the back as well, including the motor driver.


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#7 Juan Lima

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Posted 10 January 2014 - 09:35 PM

 

Eg If monitor is above battery CG, Camera CG is allways behind center post for Dinamic Balance. Usually 3/4 inch behind center post for bigger rigs.
Why did you take Lens Nodal Point as a reference?


Thats a pretty huge generalization. And often not true.

Nodal is good because when doing shots with stong veticals your tilt is exactly that a tilt. Not a arc

 

 

It was a generalization. I've never paid attention in the past to the nodal point of the lens. Very interesting! Is it something you put in practice often or only for very specific cases?


Edited by Juan Lima, 10 January 2014 - 09:35 PM.

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#8 Juan Lima

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Posted 11 January 2014 - 02:18 AM

 

 

Eg If monitor is above battery CG, Camera CG is allways behind center post for Dinamic Balance. Usually 3/4 inch behind center post for bigger rigs.
Why did you take Lens Nodal Point as a reference?


Thats a pretty huge generalization. And often not true.

Nodal is good because when doing shots with stong veticals your tilt is exactly that a tilt. Not a arc

 

 

It was a generalization. I've never paid attention in the past to the nodal point of the lens. Very interesting! Is it something you put in practice often or only for very specific cases?

 

I meant for specific shots, no specific cases! Sorry


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#9 Katerina Diakoyanni

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Posted 11 January 2014 - 08:14 AM

Nodal is good, because when doing shots with strong verticals your tilt is exactly that, a tilt. Not a arc.

 

Precisely! Thank you all for your answers!

 

In both setups, the total length of the camera was the same. But on the first one the sensor was 4 inches in front of the gimbal, and on the second one, the sensor was 4 inches behind the gimbal. Although inertia-wise the response was the same, panning and -especially- tilting felt completely different from one setup to the other.

 

Again, not a big issue, just a small observation.


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#10 thomas-english

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Posted 11 January 2014 - 03:09 PM

This kinda stuff is only remotely measurable if our subject is under 10ft away and far more critical if we are in the 1ft or 2ft range. 


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#11 Charles Papert

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Posted 11 January 2014 - 04:03 PM

 


Nodal is good because when doing shots with stong veticals your tilt is exactly that a tilt. Not a arc

 

 

Eric--if one is considering pans, tilts and rolls being executed purely from the gimbal (i.e. excluding the idea of compensating laterally via booming and sidestepping), wouldn't the only possible nodal move be a pan, if the focal point is directly above the gimbal? Wouldn't tilts and rolls have to involve an arc since there is always going to be distance between the gimbal and focal point?


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#12 JamieSilverstein

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Posted 18 January 2014 - 04:47 PM

I have to agree with Charles' question/observation.  The only nodal move in the ideal world would be a pan.  All other moves would be arcs simply because they revolve around the gimbal.  Panning is the only move that revolves around the focal plane.

HOWEVER, regardless of those realities, in my operating, every pan and every tilt requires adjustments of the height, hand, body, frame, etc.,  all of which are almost unconscious moves working to better the frame.  For me and my modest operating skills, the better the static and dynamic balance, the better tuned the arm, and the better my personal condition at the time of the shot, the less I have to concentrate on the mechanics and ultimately the better the shot, regardless of nodal plane.


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