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Actually,

 

It is steadicam related so it does have a place here. All steadicam operators should be aware of this if you aren't. Any wireless transmitter such as a modulus placed up against or near a video camera can cause severe interference with your video signal going to tape. That includes HD cameras which many of us have and will be using in the times to come. It is not a video termination issue. You have a powerful RF transmitter pumping out RF energy sitting up against a video recorder with a plastic housing and most of the time, no shielding. Even if you can get the modulus away from the camera at the bottom of the rig, that is no guarantee that you won't have problems. Always do a test first. Again, if you are shooting with an HD Cinealta, Varicam, or any other tape based system, and you are using a modulus or other RF Video transmitter, you are in danger of a screwed up image put to tape that may have little or no hope of being fixed and guess who they will blame. The steadicam operator with the video transmitter.

 

Also, this goes for your Bartech or other focus receiver. I recently saw an operator with their modulus literally velcroed to their Bartech receiver and then wondered why they were having problems with the Bartech. I consider this type of topic to be a great use of the steadicamforum bandwidth. If any of you just learned something that you did not know and it saves you the embarrassment of screwing up a productions' valuable footage, then it is my opinion that it is an important topic for this forum. But of course, it is just an opinion.

 

Grayson Grant Austin

Steadicam Owner/Operator

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Grayson, I second that, I thought already that Michael was a bit harsh over this question.

There have been other post with less relevancy than this, lately.

 

I have seen a lot of interference with transmitters, receivers and video equipment. It is indeed something we all have to be aware of.

Specially, the transmitters in the lower frequencies, like the Modulus can seriously affect other electronics and recordings.

At least, that´s my experience. With the Ghz range of transmitters, there is less chance (but not completely.)

 

Rob van Gelder, Bangkok, Thailand

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Guys the only reason I pointed that out is because the guy said he's not a steadicam operator, but shoots Betacam.

Going to a steadicam forum as a non-steadicam operator to ask a question about a piece of equipment that's not part of a steadicam (granted we use it) seemed a bit odd.

Just like we wouldn't call Plus 8 video or CIT to ask them a question about our Steadicam, even though we use their gear on our steadicams.

 

But I guess there is an "off topic" area of this forum too.

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I do agree that this is an issue that all Steadicam Ops should be aware of, since it often is their transmitter that is being integrated into a production's camera package and it is the Steadicam Op's responsibility that his/her gear doesn't screw up the camera or the recording.

 

I would be very careful using a Modulus on a Betacam with its analog recording. Digital formats are better protected. I use my Modulus on my JVC DV500 all the time with no problem. But my first suggestion to the original poster (and to anyone else having this problem) would be to add the -10db pad to the transmitter's antenna. It should be supplied with your Modulus and will reduce the transmitter's output, helping with some interference problems.

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Hey Mitch,

 

How are you doing? Good I hope. You must have a better JVC than most because I have seen this very problem with that very model of camera. Also with the Sony DVCAM camcorder models as well as digital betacam and analog formats. I will say that it was more subtle in the digital formats but still there and still unuseable and unfixable. I usually test it with every video format and camera model I encounter just for the heck of it but usually end up not using it as even slightly there stuff that you can't see on a field monitor gets seen by the editor/post engineer who then bitches to the producers. The horrible part is that it usually does not show up in the transmitted signal and is many times difficult to see on your rig monitor so do your testing with a hardline cable out to your field monitor while your transmitter is on and sometimes not even that shows up. Do a record to tape with the transmitter on and then do a playback test hardlined with the transmitter off. As with all RF voodoo some individual cameras might not get hit and some modulus may not be a problem but I just don't risk it anymore as it can be fine one moment and then crap the next. HD DPs are becoming aware of this issue lately and are starting to resist having transmitters anywhere near the HD camera. God help us all. Pray for easily available fiber optic rentals.

 

Oh, for a fun experiment, fire up your Bartechs and then move your modulus close to the receiver and/or motor and watch for your motor to shift position (Some may not be as susceptible). This is why it is important to seperate any RF components. Imagine if an assistant were to mark the Bartech for the lens and then switch on a modulus that was too close. The bartech might still work like the trooper it is but the marks would then be off. Something to think about.

 

Grayson Grant Austin

Steadicam Owner/Operator

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Hi,

 

Follow focus receivers tend to be just that - receivers; so don't transmit potentially interfering RF around the sled; that being said some follow focus units are bi-directional (Scorpio, ARRI, Prestons latest MDR-2, Cmotion) but operate at 2.4GHz.

 

The video transmitter (especially the Modulus without the 10dB pad) generates interference in two main ways. [1] direct RF - it gets into sensitive RF analog electronics (such as the tape heads in a transport), [2] it finds a semiconductor junction and this acts like an AM radio receiver and demodulates the RF into a low frequency signal which is bad news.

 

AM video transmitters (Modulus and kin) are the worst for this, FM (microwave) are much better because the output power stays constant. There is a ray of light though, there is a basic law in RF (the inverse square law) that says that as you double the distance away from the transmitter you divide the effective power by 4. So if you can double the distance your video transmitter is from the 'victim' you will divide the interfering signal by 4 (and so on...).

 

DVCAM will be less susceptible to interference due in-part to the physical size of the units (and lack of long lengths of internal wiring), and the excellent error correction required by the compression systems. Betacam SP contains masses of sensitive analog electonics, long lengths of wiring and plenty of RF ingress points....

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Michael wrote:

Going to a steadicam forum as a non-steadicam operator to ask a question about a piece of equipment that's not part of a steadicam (granted we use it) seemed a bit odd.

 

 

 

*** I think that a question about a piece of equipment that almost everybody uses in our trade (in several shapes) is a very valuable question.

It doesn´t really matter if the question came from a newby, a seasoned op. or another cameraperson!

 

I mean, if the question is really bullshit, I think people would not react to it and it dies away.

 

You were acting as a forum-moderator here and there is no real reason to do so, unless we start getting spam messages and such!

 

Rob van Gelder, Bangkok, Thailand

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I just finished a 6 month shoot on a DigiBetacam, using my Modulus 3000 on the Steadicam, and we didn't have any problems with RF hitting the tapeheads. We used the -10db pad about 20% of the time, only when the rig was close to the director's monitor and the monitor fluttered from too much signal. We mounted the Modulus on top of the lomode plate, except when in lomode when it went between the bottom battery and the sled (PRO 2).

 

The show is now airing and I've watched the first 8 episodes. I don't see any difference in quality of the Steadicam and non-Steadicam shots.

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Hi Rusty, havn't seen you in a long time!!

Have any of you had problems with onboard recorders? This is somthing I haven't used much, but I have an upcoming job where the dir. wants both transmission and DV tape for on set editing, which he doesn't want to go thru the transmission process?

Are some recorders less suseptible? ie Rusty's digibeta....

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I believe this is more an issue of the individual Modulus more than the individual video deck. The Modulus is a notoriously "dirty" unit; just have fun going through the UHF band and counting the additional bleed-through channels and harmonics. Perhaps the people here having issues own particularly nasty transmitters.

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Ghosting???? Almost impossible for a video transmitter to cause this on tape. Some noise, mabye. Chances of seeing any iterference on an HD camera/recorder are slim to none. If you have a dirty broadcast, your gona blow out your audio guys rf stuff before you see it on tape.

 

Jeff

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