Bluescreen with SDX900

B. Schultz · August 30, 2004

I am going to do my first SDX900 bluescreen shoot next week. I will be shooting at 30P which is what I do for HD shoots in bluescreen. I find that this is very helpful in compositing after transfer, because all the frames are there. I am wondering if there might be any helpful feedback concerning the camera settings etc. for a green/bluescreen shoot.

The workflow will be to transfer the camera material from 30P to 60i DigiBeta tape for compositing. I have done this many times from HD Varicam or Sony tapes, and I'm just wondering if there is anything special I might need to know that's different with this SDX900 camera.

I'm assuming that a straight SDI transfer from DVCPRO50 to Digibeta will yield a near-identical clone to composite with.

Phil Rhodes · August 30, 2004

Hi,

Two points:

- What is your delivery frame rate? If it is 24p, shoot 24p. If it is 60i, shoot 60i. The post people should be able to deal with it whatever and it should not affect the quality of any comps. If it does, someone is doing something stupid.

- You should avoid recompressing your material. If you cannot post on DVCPRO-50, look around at least for somewhere that'll do it as D5 or some other form of uncompressed images.

Phil

David Mullen ASC · August 30, 2004

Well, if the final product is 60i, I don't see a problem with 30P versus 60i -- the only difference is the "film look" from progressive scan capture of 30P. Otherwise, since both are stored as 60i, the only difference is that with the 30P capture, two fields will be identical. With 60i capture, each field is a new motion sample.

As for converting DVCPRO-50 to Digi-Beta, is it really necessary? Couldn't you just import the DVCPRO-50 into your compositing system?

B. Schultz · August 31, 2004

Shooting 30P is designed to accomodate the 60i cross-convert. The compositing will be done on an Avid system with SDI input and a DigiBeta deck, so the transfer to 60i will be done to Digi, then input into the NLE.

I was more questioning the artifact issue of 3:3:1 compression. I have no trouble compositing from bluescreen DigiBeta originals, but that is 2:1 compression. Just feeling out the community to see if the slight increase in compression has any noticable compositing artifact downside. My suspicion is that it does not.

Phil Rhodes · August 31, 2004

Hi,

Well, if it's a dramatic production and you're after progressive scan there should be no reason not to shoot 24P, even if that means you end up with 3:2 on the digibeta. Honestly if they can't deal with that find someone who can.

I'm betting that going from DVCPRO-50 to Digibeta will incur a loss. Digibeta is not completely transparent. Very nearly, but not completely.

Phil

John Morrison · August 31, 2004

I thought DVC-Pro50 was 4:2:2 color space.

If your camera has the sdi option you can load the footage to your editor via the camera's sdi output. I agree will all those who've said not to transfer to digi-beta then to your avid, even though it all stays digital, the less stops on the journey the better. As far as the 24p for compositing it is a pain in the rear to reverse tele-cine the footage & then composite especially if the final product is going to wind up 60 i ntsc. The 30p may be the way to go to avoid the reverse tele-cine step.

Phil Rhodes · August 31, 2004

Hi,

> I thought DVC-Pro50 was 4:2:2 color space.

It is.

> If your camera has the sdi option...

Which the SDX-900 does.

> As far as the 24p for compositing it is a pain in the rear to reverse tele-cine..

Personally I think it shouldn't be. You should be able to treat it as interlaced and just deal with a small amount of duplicate rendering if it's that big of a deal. But seriously, I would be dismayed to find that most places couldn't deal with this (but then again I don't have to here.)

Phil

cbolton · September 3, 2004

Just as a side I thought this might be useful. I am fairly sure one can out put a non DV compressed 10bit SDI stream out of the AJ-SDX900 camera. As long as your have the SDI option. I think they call it an EE SDI out.

Any ways if this does work it means you could record straight to any digital device with a Non Compressed SDI input with a full 10bit 4:2:2 color space with NO COMPRESSION. That would just be lovely.

I will have to take a look next time I?m working with the camera.

Good Luck on the Chroma stuff.

Cheers

Cbolton

PS ? Are you using any Cine Gamma/ chroma setups, and did you consider the progressive or interlace setup in the camera?

B. Schultz · September 3, 2004

As far as the 24P vs 30P issue is concerned - it is always better to have all of your frame information as original information and even more importantly having all of your frames intact rather than making 6 up from the 24 existing. This has ramifications in compositing because now there is the potential for artifact creation which will impact the keyer/Ultimatte's edge selection. So shooting 30P eliminates this completely and doesn't compromise the "film look" of progressive. I use the cinegamma option when I have highlight issues and on the Varicam I generally stay with the Film Menu at Video Rec to increase my gamma for normal shots. I'm still figuring out what this translates to on the SDX900, I think it means don't use the "filmlike" menu settings unless highlight suppression is needed.

Transfer via SDI is not an option on this job, although I do have the SDI option on the camera. Post will be done at a distant facility, but I will mention the ability to use a DVCPRO50 VTR with SDI to input into NLE.

Thanks for everyone's input.

Phil Rhodes · September 3, 2004

Hi,

> As far as the 24P vs 30P issue is concerned - it is always better to have all of

> your frame information as original information

They shouldn't be touching it until they've ITK'd it anyway. This should never be an issue. Really, seriously - if they can't deal with this, then find someone who can. This is completely standard procedure. It isn't even terribly important that you understand it, so long as the post house understand it. If they do not, and the reason you need to understand it is so you can explain it to them, then you need to find a more competent post house. This smacks terribly of video people trying to do film effects.

Phil

Scott Rachal · November 18, 2004

We use both DVCPRO50, AVID Meridien/SDI and Digibeta,and you needn't worry about the transfer as long as you use the SDI out of the DVCPRO deck into the D-Beta deck. I've done this often and the results never dissapoint.

-crow