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upgrade from PRO GPI regarding HD-SDI capabilities


Frederic Chamberland

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I prefer the green screen, but I admit I've only tried an LCD a few times. I think I'll get a 6" cinemonitor soon and start playing with it.

 

I was talking about a down-converted image vrs a true hd image -- it'll obviously be a better/clearer picture, but is there another reason? Sometime too much info can hinder, as can a monitor that is too big. If I shot alot of hd I guess I'd want to own my own down-converter and maybe it would be more important for me. I far prefer an optical viewfinder when on the dolly, but when running around in bright sunlight or doing really fast moves, all I've ever needed was a nice bright contrasty image so I can keep the actors in the box.

 

LCD tech is getting so good nowadays, the viewing angle is not much of an issue for most shots and many can be seen in bright sunlight. I did the last few months of Jericho with that pos f-900 and a down-converted signal, didn't have any problems (frame delay?) except power supply with my old pro batts.

 

rb

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The HD-SDI Loom

 

(snip)

 

We expect to receive our first batch in about three weeks, whereupon we will conduct a series of tests (both inhouse and independent testers) to ensure our standards have been met by this manufacturer. Assuming the results are positive we expect to be available to ship the looms before Christmas.

 

(snip)

 

 

This is a quick update because ... it has been a long three weeks ...

 

We are sorry that this process has taken this long. We received the samples of the first batch which were of a very impressive, high quality cable, however it was not ideal for our needs.

 

We found that when the centrepost length was adjusted, occasionally the loom grabbed the inside of the centre-post and this tended to restrict the movement while making the adjustment.

 

We, in consultation with the manufacturer, have agreed on a new material for the outer sheath to cover the cables. The new material will overcome this problem, and new samples have been ordered.

 

We expect the new samples, to arrive shortly. We will then need to repeat our testing to confirm the high standard has been retained and the performance has been improved.

 

We will keep you informed of the progress.

 

Kind regards,

 

Hugo Langer

Steadyrig

T/A Rig Engineering

 

admin@steadyrig.com

+61 3 9898-6298

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Hugo,

 

What gauge cable will you be using for the power lines if you are replacing the wiring loom? Are you keeping the original 8-pin Lemo and adding a BNC for HD-SDI (that requires mods to the upper and lower junction boxes) or did you magicly find a way to incorporate it into the Lemo?

 

Thanks!

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Hugo,

 

What gauge cable will you be using for the power lines if you are replacing the wiring loom? Are you keeping the original 8-pin Lemo and adding a BNC for HD-SDI (that requires mods to the upper and lower junction boxes) or did you magicly find a way to incorporate it into the Lemo?

 

Thanks!

 

Hi Alec,

 

I am sorry it's taken so long to get back to you.

 

We have received a lot of emails that are asking similar questions and we have been in discussion with our cable manufacturer

 

One of the most popular questions we get is for additional cables incorporated into the loom to cater for the needs of additional equipment (for example, a tally light control signal) .

 

We have gone back and redesigned the loom to carry heavier guage power cables and 4 additional cables. Obviously this will necessitate a non 'industry' standard Lemo plug and socket for the additional functionality OR standard Lemo's if you do not require the additional features of the loom.

 

We will need to complete the testing as far as shielding the HD-SDI signal within the Lemo plug & socket fittings. So far we believe that Lemo's are sufficient for the purpose.

 

We will have more news to share in the New Year and this will include the detail of the specification and type and quantity of all cables within the loom.

 

For now we wish all a happy holiday and a safe New Year celebration.

 

Kind Regards,

 

Hugo.

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I have just finished working on and testing a modification to my PRO rig to get HD-SDI down the post. It required changing out the 8 pin Lemo for a special 12 pin + 1 50ohm lemo plug. The plugs are the same size so no machining was required. The new plug looks like this.

 

post-1262-1232315363_thumb.png

 

I had to completely rewire both my topstage and Lower Junction as well as install a Panel Mount BNC jack in both (crimp design not solder) I used two pins each for the Camera and Aux power runs, and single pins for Composite video and Video power. HD-SDI uses 75ohm cables and connectors but the two 50 ohm plugs don't seem to affect the signal at all. I tested it at PANAVISION with the HD tech and the signal looked fine on the scope.

 

The pins on the plug are only good for 5 amps each, but because two are used per run I get 10 amps for camera and 10 amps for Aux power, the same as the breakers in the rig. I'm also using a Y cable (with diodes to prevent cross charging) to power HD cameras, effectively giving me 20 amps.

 

The hardest part was finding an appropriate coiled cable for the post, I use a 4 piece extendable. I was able to source out a cable that was appropriate but not perfect. I had to use multiple cores twisted together for the power runs to achieve the equivalent of 17AWG for each. The company that makes the cable would require an order of at least 50 (at $75 a piece) to make it to spec. I figure 4x14AWG (camera & Aux power), 2x20AWG (video power) and 2x RG179 (HD-SDI and Composite Video) would be perfect for most needs. If enough people are interested in upgrading their system perhaps we could have a run done. Hopefully everyone would want 2 and therefore only 25 people would have to commit.

 

If you are interested please let me know by way of replies and if it seems we have enough I'll talk to the company about putting together a quote with exact specs.

 

IAIN

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I am definitely interested although I would also like to hear about what Hugo is working on.

 

Would the company add the Lemo connectors as well? Seems like hooking up the BNC and all those connectors could be difficult.

 

~Jess

Edited by Jess Haas
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The company would NOT add the connectors, they will just make the coiled cable to spec. You would have to find someone to do all the soldering and wiring for you. Keep in mind that both the Upper and Lower Junction Boxes have to be modified as well, adding the BNC plug and changing out the Lemo jacks.

Edited by Iain Baird
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HD-SDI uses 75ohm cables and connectors but the two 50 ohm plugs don't seem to affect the signal at all. I tested it at PANAVISION with the HD tech and the signal looked fine on the scope.

 

50 ohms is LESS resistance then 75 ohms, so the 50 ohm connectors are over-spec, which is good. If you look at a cross section of 50 ohm cable it has a much thicker copper core then 75 ohm cable.

 

Your commitment to making this work is commendable, it's a lot of work to do all that you have done. Hope it all works out for you.

 

-Matt

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Thanks for the clarification Matt, I should have mention that part. The HD tech explained that to me that if anything the signal would be brighter, however we didn't notice any difference on his monitor or scope. Perhaps because it's only for such a short amount of the run it doesn't affect the signal. Both the Panel Mount Jacks I'm using are 75ohm as is the RG179 cable.

 

Although I would prefer a better post cable to the one I'm using this has been tested and works. I have an HD monitor (Tiffen) but I use it in composite mode because my frameline generator and Level don't work on the HD signal. I'm sure eventually I'll have an HD monitor with built in Level and framelines but in the meantime I'm planning on buying the CAMWAVE and wanted the weight below the gimbal.

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Soldering and the modifications really aren't a problem for me, it just seems like that Lemo with all of those connectors and the BNC are going to be a pain.

 

~Jess

 

Indeed Jess, many hours!! And for me, add to that, not being positive it would work.

 

IAIN

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50 ohms is LESS resistance then 75 ohms, so the 50 ohm connectors are over-spec, which is good. If you look at a cross section of 50 ohm cable it has a much thicker copper core then 75 ohm cable.

Not exactly. 50ohm and 75ohm don't refer to the electrical resistance they refer to the characteristic impedance which is determined by the spacing of the conductors and the insulation between them. Video signals use a 75ohm system. If you try to send it over a 50ohm cable it will not work better. When the 75ohm signal gets to the 50ohm connection some of the signal will be reflected back by the mismatch which can lead to a weaker signal and ghosting. This will happen again at the other end. While I wouldn't go using 100ft runs of 50ohm cable for a video signal I doubt that the 50ohm connectors in this instance are going to be a problem.

 

~Jess

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50 ohms is LESS resistance then 75 ohms, so the 50 ohm connectors are over-spec, which is good. If you look at a cross section of 50 ohm cable it has a much thicker copper core then 75 ohm cable.

Not exactly. 50ohm and 75ohm don't refer to the electrical resistance they refer to the characteristic impedance which is determined by the spacing of the conductors and the insulation between them. Video signals use a 75ohm system. If you try to send it over a 50ohm cable it will not work better. When the 75ohm signal gets to the 50ohm connection some of the signal will be reflected back by the mismatch which can lead to a weaker signal and ghosting. This will happen again at the other end. While I wouldn't go using 100ft runs of 50ohm cable for a video signal I doubt that the 50ohm connectors in this instance are going to be a problem.

 

~Jess

 

 

Obviously the ideal would have been to use a 75ohm connector. However the only plug Lemo makes with a 75ohm connection and at least 8 pins is sized 5B, way too big for consideration.

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