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Preston Remote Focus Interference on G2 receivers?


David Fleming

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Recently I was working on a job were I mixed and boomed sometimes working very close to the camera . During quiet passages I noticed a very low level ticking sound which I assumed may have been coming from the Preston remote follow focus in use. Is this something other people have experienced before. Will using higher quality receivers help to eliminate the noise or is it all problem with all systems?

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" Will using higher quality receivers help  "

it depends!

was the ticking actually audible (you could hear it with your ears)?? 

it could be getting in through the microphone (capsule or electronics) itself or be RF that is getting into the RX.  A number of us say that this business is mostly about problem solving, and this is a problem for you to hone your problem solving skills on... try alternatives: different mic's, different cables, different frequencies, different positions.  You might want to get the SC involved, as it is her/his problem, too (you are, after all, making the same movie, and the AC can also try some alternatives.  find out what combination works best for both of you...

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  • 1 year later...

We are currently running into the same issues and have tried a multitude of attempted fixes, all to no avail.

We have discovered that, on a long walk and talk for example, that if the camera gets at all between the cart and the talent, we take hits.

it is highly frustrating and I wonder if anyone has found a reasonable solution .....

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On a recent job we had 3 handheld cameras all with Preston units on them it was frustrating and range was worse in small enclosed spaces. We were shooting in a cramp high rise I was in the hallway less then 20 feet away and was having issues. I moved the antenna mast a few feet over and managed to get rid of it. Funny though was my boom op was standing right next the the camera within about 2 feet with a 250mw tx on his belt and it was causing the Preston to creep on its own. Camera Dept was having a fit convinced it was someone texting during the take causing it. After not getting any help from camera at all for weeks with the issues we decided just to return the favor and do nothing about it. Surprisingly they used a whip and pulled focus the old fashion way.

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I'm not sure about the g2 receivers particularly, but these wireless camera devices (Arri and Preston L.C.S etc) do not seem to be particularly robust when it comes to RF inference/pollution and indeed their own operation.

I know they get affected by strong 2.4ghz signals and stop functioning. (bye bye my lovely old video sender...) Although they have capability to switch frequency (this week the system we're using has 'channels 0-9') there is no information - nor have I ever met anyone in a camera dept who can tell me - which frequencies they occupy. Its just seemingly another toy to them and its use and is becoming increasingly 'standard' in camera kit packages on shoots where remote lens control is not even necessary.

Slighty off topic, but this is one thing that stops me investigating a whole Zaxcom IFB/ timecode system which would be perfect for me to use but it functions on 2.4ghz and I'd be worried about intererences between all these kinds of devices - has anyone experienced this at all?? Also similar worries about DITs setting up iPad networks for 'dailies' becoming much more common and blotting that whole area of the spectrum. The sound department needs rf priority on set to operate effectively as a small department. Camera can't interfere with this because of poorly designed equipment IMHO.

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I *think* I experienced this interference on a job where the G2 was receiving scratch audio on the camera. We never nailed it down because it was a Red Epic shoot, and the camera didn't do playback. Way too much time to record, then run the clip to the DIT, then..... yeah. We figured it was a scratch track for dailies we didn't think anyone was actually watching before syncing was being done. I was using a SB-3 for TC and that was flawless.

With the Zaxcom ERX, if it doesn't receive TC, there is an internal clock to keep going. The audio *may* be compromised though, so try to test that. Odds are the issue is when the AC changes focus/iris/zoom, so that tiny burst of RF should not keep the TC from getting updates. The transmitter is with the AC, so it also may matter how close they are to the RX, maybe you can mount it on the non-AC side of the camera. I would think a video sender is a much bigger issue since it is on the camera (inches from our camera mounted RXs), and running non-stop. As for us causing a problem, I wonder if a QRX100 transmitting the IFB signal while mounted on the camera would interfere with a Preston or something. This might be a reason to get a handheld scanner and have the AC use it so you can nail down where they are. I have definitely been on jobs where some mystery source of RF caused the focus to go bonkers. We spent 3 weeks in the same house and sometimes it just went crazy, but most of the time it was ok. Camera was using a Varizoom (if I remember right). I know very little about those things, but somebody in camera dept said they are more prone to interference than some of the other ones.

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On a related topic, the camera department on my current movie is using a Preston unit that is producing an audible scraping sound. Audible as in you can hear it with naked ears, so it's not an RF thing. It's loud enough to ruin quiet takes. Has anyone encountered this before?

I have heard varizooms before. Usually the RED camera is so loud that it drowns everything else out. :/

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I've heard the Preston's moters whining sometimes. It has to do with the type of moter they use(stepper I think rather than servo) which uses current to hold the moter where it is when not in motion. Though I have only heard this sound on older rental house Preston's never heard it with a new/well maintained one.

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Though I have only heard this sound on older rental house Preston's never heard it with a new/well maintained one.

Strange. They just got a brand new Preston yesterday (they were having some other issues with the old one), and the new one was even louder. They said they'd try switching out the motor, but since we're shooting exteriors today, it's hard to tell if that made a difference.

We're shooting on the Alexa, by the way, so fan noise isn't really an issue.

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