Home of Professional Cinematography since 1996

Wireless Video Interference

Published : 8th December 2003


Hello,

I had a shoot last week where we flew my Arri 35-3 on a steadicam and used a Modulus video transmitter [like we have used many times].

Whenever the 35-3 turned on, we got a horrible picture...rolling & cutting video. When the camera stopped and the shutter parked, the picture was fine. When we used the same Modulus on a Moviecam, it was fine.

I suspect that the Arri 35-3's motor is causing the video signals disruption.

Does anyone know if this is a common problem?

Cheers,
Jeff Barklage
USA DP



Jeff Barklage writes :

>I had a shoot last week where we flew my Arri 35-3 on a steadicam and >used a Modulus video transmitter [like we have used many times].

It's not common, but it does happen. It may be RF interference from the motor, but it may also be that the Steadicam’ s video wiring is adding to the problem.

Some older taps were very prone to this problem.

Try separate power supplies for the camera and tap and see if the problem goes away.

It may also be time to get your motor cleaned and tuned.

Brian Heller
IA 600 DP



Jeff Barklage wrote :

>Whenever the 35-3 turned on, we got a horrible picture...rolling & cutting >video.

Sounds like the motor was making a mess of the power. I had a similar but probably not as bad problem flying my SR on my steadicam. I threw a capacitor across the + & - of the power leads to the tap and that helped tremendously but did not cure the problem completely.

My .02 is that it is a problem that involves motor interference interacting with the high intensity steadicam monitors.

Mark Smith



This was a fairly common problem with older Arri cameras.

The solution is to power the Modulus separately from the camera. It's also a good idea to move the Modulus on the rig so that it is physically as far from the camera motor as possible.

Mitch Gross
NYC DP



Jeff Barklage wrote :

> When the camera stopped and the shutter parked, the picture was fine.

This may be a dumb question, but were you powering the tap from the camera, or the same battery that powered the camera?

I've seen that cause the problems you describe.

Steven Gladstone
Cinematographer - Gladstone Films
Cinematography Mailing List - East Coast List Administrator
Better off Broadcast (B.O.B.)
New York, U.S.A.



Hello,

Steven asked this question [in response to my post regarding video assist interference with a 35-3 on a Steadicam] :

>This may be a dumb question, but were you powering the tap from the >camera, or the same battery that powered the camera? I've seen that >cause the problems you describe.

Yes, the Modulus and the CEI Color-V are all powered from the same 3-way Fischer splitter box attached to the camera. I was assuming that a common ground, between all 3 electrical components: camera, tap & transmitter, would help matters.

It doesn't.

What's weird is that the picture is beautiful while the camera is stopped, but as soon as the motor spins, it goes bad.

I check to make sure the voltage drop wasn't the issue...it's not. So, I am guessing that it is the motor's brushes?

I'll try bench testing with the camera off any mount and with separate power supplies for the transmitter & body.

Cheers,
Jeff Barklage, s.o.c.
US based DP
www.barklage.com



Jeff Barklage wrote :

>When we used the same Modulus on a Moviecam, it was fine. I suspect >that the Arri 35-3's motor is causing the video signals disruption.

Yes it is Jeff,

That's why the GPI PRO has a separate video side that powers the video tap and carries the signal.

Eric Fletcher SOC
Steadicam/"A" Camera Operator
Los Angeles, CA USA



Hi,

>That's why the GPI PRO has a separate video side that powers the video >tap and carries the signal.

It should be pointed out that GPI's outfit is not the only Steadicam-alike system which can or does have splittable power.

Phil Rhodes
Video camera/edit
London