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Dymanic Balance


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#1 Amelia Cutadean

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Posted 04 April 2009 - 04:37 PM

Is dynamic balance effected by the position of the camera on the sled. I understand as a rule of thumb one finds the center of balance on the camera and places this about 3/4 of an inch behind the center post. If the rig is horribly off balance my first instinct is to make a large adjustment on the sled moving the camera and plate forward to a place near the center of balance and then make my fine adjustments side to side and fore and aft. I am wondering if dynamic balance is effected by this and must the center of gravity of the camera be over the center post for dynamic balance to work . I ask this as I am switching from practicing in low mode (balanced dynamically well) to switching back to normal operation. As I moved the gimbel and adjusted my monitor to a higher position my rig was horribly off balance which I did expect since I moved my monitor but am wondering if making a gross adjustment of the camera position away from the 3/4 inch behind the pole before fine adjustments is the way to go.

Amelia
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#2 Tom Bonsignore

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Posted 04 April 2009 - 07:26 PM

Hi Amelia,

I have the canon xh-a1 and several accessories attached to it. When I first tried balancing it I noticed putting the camera's center of gravity right over the post seemed to work better. When I tried it with it 3/4 " behind the post I never was able to achieve dynamic balance. I think the 3/4" rule is just a starting point.

I would try getting it with the camera mounted at different positions, just make sure that you have the camera's fore, aft, left and right CG located fairly well.

It may take some patience. However I have also learned that going crazy with dynamic balance is not necessary. As long as the camera is fairly stable when you spin it you should be good to go.
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#3 Jerry Holway

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Posted 05 April 2009 - 10:33 AM

Amelia-

As the monitor c.g rises up from the battery c.g (all other things being equal), the camera c.g. moves t the rear and the battery moves forward for dynamic balance. Each situation is unique.

If you have a Pilot, with the monitor raised up very little, the camera c.g. is going to be close to the centerline of the centerpost when in dynamic and static balance.

3/4ths of an inch is only a guideline - and a guideline for BIG rigs, with monitors raised about 1/4 of the way to the camera c.g., and with 25-30 pound cameras...

Read the book, download the dynamic balance primer and the Excel spreadsheet (my site or Tiffen's) and plug in some new measurements and numbers for your sled.

Make those little drawings!

Jerry
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#4 Amelia Cutadean

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Posted 05 April 2009 - 11:04 AM

Thanks Jerry, I'll do that. Whether the camera needed to stay closest to it's starting position as possible is what I was trying to figure out. You have answered my question. I understand why dynamic balance works but I definately need to read the book some more, download the primer,and make the drawings (I do remember you saying that, & you were right!) to wrap my head around the entire process.

Amelia
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#5 Amelia Cutadean

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Posted 05 April 2009 - 12:57 PM

An addendum to my previous post. I read about dynamic balance using The Steadicam Operator's Handbook and have gotten a better understanding of it. It is basically a rotation. If I am moving my monitor up, or if thinking of it as happening within a circle, then clockwise, the camera then moves in a clockwise direction and the batteries, likewise do the same. If I were to lower the monitor then the opposite would occur in a counter clockwise direction. I'm not sure why this didn't occur to me before so thanks for the input as it seems I was missing the obvious.

Amelia
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