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Best Solution for Blue Screen Project


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#1 Frank Vinas

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Posted 02 September 2010 - 12:46 AM

I' m shooting a technology segment for a local network in Dominican Republic and have encounter a few problems. I used the in studio camera (SONY 537 CA 720p) to shoot a blue screen scene that is going to be aired in 16 channels locally. I've posted an 8 second take so you guys can see it and make comments. The problems I've encountered are: too much grain on the image after we did the output. When we cleaned the matte the subject had an obvious flickering on his hair and some parts on the body were still a bit dirty. The subject has spiked hair and the blue screen can be seen through it and is impossible to clean the hair section .
Cinematography is still in an embryo state in this country but is growing slowlly eventhough there is no schools. We want to make the best show we can w/ what we got.
Networks don't have capability to air in HD so most of the stuff they shoot here is aired in SD.
I'm re-shooting all the bluescreen parts with a SONY HVR A1U or a CANNON XH A1. I have a cople questions regarding camara and lighting. What would be the best settings to shoot w/ the SONY or the CANNON?( I had never shot w/ nither) I know you guys probably have a lot of expirience shooting w/ these cameras on blue screens so any tips would be greatly apreciated. Another question that ran into my mind was if the BLUE was not the correct blue for the bluescreen? can I capture HD and down converted in premier CS4 to SD?

http://www.youtube.c...du?feature=mhum

Frank Vinas
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#2 Ram Shani

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Posted 02 September 2010 - 01:05 AM

from what i see

- your screen maybe is light to strong and reflect on your subject on the edges make it more hard to cut it
light the screen a 1-stop under the key light and put your subject as far as you can from the screen
- use more back light on the test it's hard to say if you used any back light at all
if you will put half CTO on it it will help with the cleaning of the screen
- use better camera with better codec like hvx200 which has 4:2:2 colour sub sampling which make it easier to cut
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#3 Scott Fritzshall

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Posted 02 September 2010 - 03:10 AM

Actually, that's not half bad for a blue screen shot. You should be able to get good results from that. It looks like that camera is XDCam, is that correct? First of all, make sure that you're capturing it properly, and that you're working with uncompressed images when you do your keying. The camera is already applying all sorts of compression and screwing with the image in various ways, and this may be part of what is tripping you up. Make certain that you don't have the sharpening turned on in the camera settings (sometimes called "detail"), because this can give you edge artifacts that can be almost impossible to get rid of.

I'm guessing, though, that most of your problem is probably just in how you're doing the keying, if you don't have experienced people doing it. Don't try to key the entire image at once. You may get settings that work for the hair that don't work for the rest of the body, for instance. Pull multiple keys and draw rotoscope shapes to use to combine them. You can add the results of keys on top of each other as well. A common technique is to get a key that just works for the edges, but may have holes on the inside, and then get another key that is really solid inside but doesn't extend out to the edges, and add them on top of each other.

I don't think that you need to change the lighting or add a backlight to your subject. Your lighting should match the conditions that would be present in the background you're using. Just try to keep your subject's lights off of the screen.

If you can post a single uncompressed frame, I can take a crack at keying it and see if there are any other problems.
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#4 Frank Vinas

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Posted 05 September 2010 - 01:40 PM

Ram

Thanks for the input you were right. The foreground lights were crossing to the blue screen, plus I didn't have a kick on the subject. I think that hurt us a lot. But we re-rigged with a green screen we purchased at an old textile distributer here and we found some one who had spared arri lights / silks and a chimera also. The green screen was at 4.0 f-stop and the subject at 3.4 and 2.8 f-stop. What was strange is that we did a pre-light test without any light arrangement and just the top florescence from the room and we cleaned the matte and it came out pretty decent so I can imagine what it will look like well lit. But the blue screen gave us so much trouble. As soon as I get the final I"ll post the before and after. For the next episode they've facilitated us a SONY Z1, i have not worked with it, what do you guys think in terms of shooting green screen? otherwise is PANASONIC DVX 100A.


from what i see

- your screen maybe is light to strong and reflect on your subject on the edges make it more hard to cut it
light the screen a 1-stop under the key light and put your subject as far as you can from the screen
- use more back light on the test it's hard to say if you used any back light at all
if you will put half CTO on it it will help with the cleaning of the screen
- use better camera with better codec like hvx200 which has 4:2:2 colour sub sampling which make it easier to cut


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