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a-minima on an ultra?


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#1 JakePollock

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Posted 05 July 2004 - 10:37 PM

Prepping a music video for next week and the production company wants to use their own a-minima; however, they had a bad experience trying to fly it on a steadicam in the past.

I've tried to think over why it wouldn't be possible and am coming up blank. obviously, weight is an issue, but nothing a few diving weights couldn't handle.

am i missing something?

the only thing i can think of is if the steadicam rental house doesn't have the proper cables to power the camera, but even if we used accessory batteries that would be fine, right? wouldn't that help add much needed ballast to the rig?

which leads me to another question, if i may. can the ultra power 12v and 24v gear at the same time? 12v camera; 24v preston?

thanks as always!

jake pollock
taipei, taiwan
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#2 Larry McConkey

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Posted 05 July 2004 - 11:47 PM

If you have the 24 volt Ultra, you actually have a 28.8 volt Nicad pack and a 100 Watt DC to DC converter that delivers 13.2 v. So you can do the math - you have a little over 7 amps available at the 13.2 volts and virtually unlimited amperage at 28.8v ("unlimited" in our world at least = Nicads can deliver 50+ amps for short periods easily). I can't imagine there would not be enough power to run the Minima on the "12v" converter (some power hungry 12 volt cameras could be a problem), but a test is the best answer as there is always the possibility of some weird problems using DC to DC converters (possible interference in the video, etc.)

If you have a more recent Ultra it has two identical 3 pin Lemos in the back either of which can deliver the "12" or "24" volts depending upon which pins are used in the connector. If you don't already have one of each check with Tiffen or Fred Davis or anyone else you use for cables. If you have an older model you may only have one 3 pin back there, so you will need to get a custom junction box or 'Y' cable made up that can split out the 12 and the 24. There is also the same "12" and "24" volts available on the small 3 pin lemo in the front which was designed for radio systems, so the inside cabling and the connector itself can't handle as much amps (maybe 2-3??). I think some Ultras where delivered with an additional power connector installed on the right side of the sled near the bottom, but this is the worst possible place to have a power cable sticking out - right where your leg is.

Larry
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#3 JakePollock

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Posted 06 July 2004 - 12:17 AM

it's the newer ultra with two lemos in back. i know that the rental house has a three pin male on one cable and a two pin male on one cable, so i presume the two pin is for 12v and the three pin is for 24v. since the camera is the production company's, i'm sure they'd be willing to lend it to me for a test.

however, are there any other issues that people have run into with flying an a-minima?

thanks,
jake pollock
taipei, taiwan
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#4 Larry McConkey

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Posted 06 July 2004 - 07:34 AM

Each stage connector has 3 pins: Pin 1 is for ground, Pin 2 is for regulated 13.2v, and Pin 3 is for battery voltage (28.8v nominal), so the mating connectors usually have only two pins in different positions for the desired voltage. This assumes a crimp style connector where you have the option of only installing the pins you need (crimp style pins can carry more current than the solder style in addition to being easier to repair). Best to ask some questions or do some testing to figure out what each cable is for.

I have never used the Minima, but the other considerations are how to mount focus/iris/zoom motors as needed. The usual solution would be a low mode plate with rods for the motors. A less ideal but still serviceable way is to use the adaptor Tiffen sells that screws onto the front of their camera mount plates which then clamps onto 15mm rods. Another workaround would be a cage which offers easy opportunity to add weights as well.

Video assist should be workable at the needed ASA setting and without too much noise when the camera is running. Remote run cable is nice to have. But the main issue would be adding enough weight for the lowest setting on the Ultra arm. I am not familiar with the camera, as I said, but any accessories like a matte box system including sliding base plate would help with weight and offer more lens motor mounting options as well. Hopefully someone with experience with the Minima will contribute...

Larry
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#5 JakePollock

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Posted 06 July 2004 - 08:26 AM

Larry,

thanks for your input. i'll test the cables at the rental house tomorrow, but even if there's an issue, we can still use separate batteries.

as far as the lens motors, the rental house engineered their own mounting plate with a screw on adaptor for 15mm rods (most likely a taiwanese "borrowing" of the tiffen adaptor).

i've got my own steel practice cage which i'll probably strip down and use to add a little ballast. another option i'm considering is using the ultra with an msb arm (taiwan only has those two kinds of steadicams).

the real kicker, though, is the production company themselves. for whatever reason in the past, they weren't able to use their camera on a steadicam (could've been the msb, but still should've been ok, right?) and now they're so certain that it can't be done. so certain, in fact, that they're not willing to let me take it to the rental house to test out unless i call the rental house and get to the bottom of whatever problem they faced who knows how many years ago.

so, if anyone can think of any possible issues, please let me know. i'd be happy to shoot this thing handheld or get them to rent an SR, but it's a real drag spending my all of my free time trying to convince this director that whatever problems they had in the past can't be worked out this time around.

jake pollock
taipei, taiwan
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#6 Jerry Holway

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Posted 06 July 2004 - 08:53 AM

Enjoy the flight!

One great thing about the A minima is the incredible height - high or low - that you can get with it and the Ultra; (I played with one of the first ones in NYC long ago...)

Add just enough weight to the sled to get the arm to work.

Add the weight to the base (diving weights work fine; Antlers OK, too) if you want the lens very high or low. Add a weight with the camera if you want a more normal range of lens heights.

I would also consider extending the monitor and battery a couple of inches further than normal to give you your "normal" feel in pan, as the A minima will give you almost no pan inertia and the rig may feel too whippy.

Jerry
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