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Back focus issue when transporting on rolling stand


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#1 Brandon Thompson

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Posted 18 March 2015 - 10:23 AM

I am currently on a show shooting on the Sony F55. We were told that last season there was a back focus issue thought to be the result of vibrations transfered to the cameras when they are moved on the rolling stands. So now we have to wear the rig when moving from sound stage to sound stage or worse the 300yds to the back lot. Theses are the typical Steadicam stands with the 8" pneumatic wheels. Has anyone experienced a problem with the F55 and back focus or with any camera and transport on the stand??

Thx
Brandon
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#2 Jess Haas SOC

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Posted 18 March 2015 - 04:34 PM

Used the F55 a good amount and rolled it around on my stand and cart with no problem. Are you using ENG style zooms with the backfocus/macro adjustment? I could see that loosening with a lot of vibration but it's also an easy fix.
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#3 brooksrobinson

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Posted 18 March 2015 - 05:06 PM

I just finished a four month run on a show using F55's out of Panavision WH. It was a hospital set with long hallways, and we had several lengthy shots per day. My 2nd AC always met me at the finish line with the stand (American 2 riser steadicam stand with American (non-inflated) wheels) so I could dock the rig on the stand as soon as we cut. He would then transport the rig on the stand back to one. We did this every day multiple times a day and never had an issue in the four months I was there. Granted, the floors of the set were flat and smooth, but there was never an issue. I'm not sure your back focus issue is coming from the rolling stand. Good luck getting to the bottom of it..

Brooks Robinson
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#4 Victor Lazaro

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Posted 18 March 2015 - 05:39 PM

What lens and adapter are you using? I haven't had any issues with vibrations and back focus either.


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#5 Brandon Thompson

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Posted 18 March 2015 - 06:33 PM

we are using the Fuji 19-90 and the Sony ff5 to PL mount.
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#6 Walter F. Rodriguez

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Posted 18 March 2015 - 07:28 PM

Why not just pull the lens and then roll the steadicam on the stand as usual?
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#7 Brandon Thompson

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Posted 19 March 2015 - 11:38 AM

ah, yes that would be the logical thing to do.  but I am on a show that is against all logic.  I assumed there are no real issues rolling the camera on a stand with pneumatic wheels.  The back focus issue in the past season probably wasn't a result of rolling the carts, but the carts had to take the blame.  


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#8 PeterAbraham

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Posted 22 March 2015 - 04:33 PM

Here's a possible answer.

 

I use a Beefy Baby Stand. I also got some studio wheels, and they are not specifically made for my stand. All well and good. But sometimes, depending on the spread of the legs when the stand has been opened and wheels locked into place, the wheels vibrate VERY violently as the rig is rolled along. Upon examination, I see that the wheel caster is not quite vertical and as the wheels are turning, they are not able to roll and adjust as the stand is moved along with a perfectly smooth rotation. Hence the vibration. Of course, it must be all three wheels since they are all locked onto the legs of my stand.

 

One game wheel might not be an issue, but three wheels vibrating rapidly is something I can easily feel- and I'm only moving my docking stand 30 feet or less.

 

Perhaps the objectionable problems last season were the result of this kind of asymmetrical force on the wheels creating rapid vibrations. See if one of the A.C.'s was on last year and remembers this artifact. They would have been pushing the rig daily, they'd remember if the wheels turned very smoothly or were problematic.

 

Oh, and I use the hard wheels. 8" pneumatic? Hell, even if they are not seated well, I'd be thinking that the vibrations would be minimized by the air in the tires. But as a global possible solution, check to see how the wheels are in terms of smooth operation.

 

Best to all,

 

Peter Abraham, S.O.C.


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