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Green screen lighting


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#1 ozkul dikici

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Posted 22 December 2010 - 04:42 AM

Hi everybody,
I am about to shoot a scene in green-box. Although I worked as an electrician and grip for few green-box shoots, this will be my first DP experience in this field, and as everybody else I want to do a good job so I need any help that I can get. With that being said, I would like to describe the scene as best as I can. I hope experienced cinematographers and gaffers out there would see my post and guide me thru challenging details of lighting the green-screen.
1) My subject (a belly dancer wearing a dress decorated with sequins) will be walking in front of the green-screen about 20-25 ft.
2) My camera will be dollying in with a 40 degree angle towards to marked meeting point with subject.(we are moving left to right)
3) My subject will stay in the frame all the time.
4) My subject will stay on the right side of the frame because as she walks; her hand moves will create a gold color silhouette of a city that appears and disappears as it follows her. (sort of the animated disney logo)
5) As we move with the camera gold color silhouette on a black background will stay on the screen for few seconds, when I met with my subject only her arm will be in the frame and a butterfly will fly around her arm and land on her hand.
6) Black background, gold silhouette and the butterfly are the only things that will be posted with CGI.
7) I have any lighting and grip equipment that I will be needing.
8) I will be using JVC 790HD
These are the things that I can think of, If you have any suggestion about a shoot like this please share with me.
Thank you,
Ozkul
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#2 bogdanovici barbu

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Posted 24 December 2010 - 02:10 PM

Hi!

Although you've provided with a pretty detailed description of your shot, I'm affraid you need to be more specific about the areas where you think you need help/advice.
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#3 ozkul dikici

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Posted 28 December 2010 - 02:02 AM

Hi!

Although you've provided with a pretty detailed description of your shot, I'm affraid you need to be more specific about the areas where you think you need help/advice.


Hi,
my main question is; what can get on the green screen? what I meant by that, when I worked with green screen we could put cutters, silks etc which would be in the frame. I have been told, as long as the subject doesn't cross between the cuter and the camera the cgi which will be posted on the green screen can cover the cuter or whatever. in that case wouldn't frames or light stands(anything like that) effect the tone of the chroma and give a hard time to post people?
thanks
Ozkul
PS: I hope my explanation is clear.
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#4 Adrian Sierkowski

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Posted 28 December 2010 - 09:36 AM

For stuff on the screen you'd need to do a garbage matte first to get rid of anything extra in the frame and then pull your green from what's remaining

If you watch this tutorial for after effects:

http://www.videocopi...rials/3d_ledge/


you'll see what you need to do to get rid of equipment in the shot.
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#5 Chris Millar

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Posted 28 December 2010 - 04:46 PM

sequins are going to reflect the green - especially around her edges ...
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#6 Deniz Coker

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Posted 28 December 2010 - 06:58 PM

Sequins popped into my head as well, I just wrapped some green screen scenes and it's always the tiny details like that which get you. Now if you're going to be moving around on a dolly, you'll need some tracking markers. I think you should really sit down with the person who will be doing the VFX. They'll probably chime in on tracking markers and such. I've used everything from tennis balls to x's made from tape. Something to be able to pull x/y movement and z depth from. I've seen people use crazy patterns on screens because it gives them variety when motion tracking. When keying, your goal is to key as little as possible. I personally do a tight garbage matte (I never enjoyed simple 8 point mattes, and you don't have to go all out and roto the shot), but trust me it'll save you time. The time you spend prepping your project before you apply a keyer will help you that much more when you actually pull a key. Also, one click keys are very very very rare and often useless. I often break people up into various parts depending on how successful my key is coming along. I like to isolate the head simply because hair often requires great detail. Then I move onto arms, sometimes fingers need more attention and areas like the arm pits. Keep in mind your shutter speed, go too slow and you'll have blur mania. Let me tell you, keyers typically hate motion blur and for control reasons, I've often left that up to VFX for these types of things anyway. But in more direct response to your question, simple things like stands, booms and such are very easily removed. Again, the goal is to shrink the green around her as close as possible, THEN key. So as long as she doesn't cross paths with any gear you're all good. If she does, you're in for some frame by frame roto work. Never fun.

Now in regards to framing, I personally like to go in tighter with green screen shots. You're isolating the person anyway so you'll get to position and frame them in a digital environment anyway. I find that going in closer gives you a nice big shot of the person and you can scale or shrink them in the environment depending on your needs; again more flexibility in post. I did have a little trouble understanding the final product, my brain's a little mushy right now but why couldn't you just shoot on a black background and rotoscope in the city? From my understanding, it seems as though it will mostly be around her arms/hands? That is pretty easy to do and would save you a nightmare of post work including reflections on her sequins and such (p.s. you might want to dull those down just for that reason). You can throw some duve on the cyc and you'll be 90% of the way there in camera. I should note, I originally come from a VFX background and since moving into more "in camera" work, I try and avoid all specialties like green screens unless absolutely necessary just because of the extra pomp and circumstance that comes with it. So that's where my views come from, just something to keep in mind. Either way, I can go on about this forever, hope you find this rant partially useable! :)
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#7 ozkul dikici

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Posted 29 December 2010 - 07:30 AM

Thank you Deniz,
Every single detail you've explained in your reply was very useful. Since you are from VFX background, the tips you gave me here might save my live(my post guy is a bit diva). If you would have little more time to spare for me, I would also like to ask you; what are the most important things to watch when I am putting my reference marks?
Thanks again for your help and time,
Ozkul Dikici
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#8 ozkul dikici

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Posted 29 December 2010 - 07:42 AM

Thanks Adrian,
Unbelievably useful video!
Ozkul Dikici
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#9 Deniz Coker

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Posted 29 December 2010 - 09:19 PM

Completely glad to help! I learned this stuff by getting it wrong so many times, I tend to ramble on so others don't make those mistakes as well! Here's a link with some pretty good advice about tracking markers:
http://www.fxguide.com/fxtips-273.html

I like using the dots but have used Xs made from green or yellow tape as well. It gives you the X,Y movement. Tennis balls on sticks can give you the Z movement, when you're moving forward. Although personally, I usually try to avoid moving the camera forward and instead when the person is keyed out, move them along the Z axis in post. It does depend on the scene but this gives me a little more control and lets me drop an environment let's say at -2000 Z behind them and when you move the CGI camera as you would a dolly, you get the proper parallax of the background and foreground in terms of how they'd react had you really been there. Use a waveform monitor for sure. You should have a thin line across the middle if the screen is evenly lit. To be honest, if the area you're shooting is pretty contained, you can focus on that, you don't have to go crazy lighting the corners of the screen behind stands and such. It can come in handy if one of them winds up in your shot but I typically make it my goal to garbage matte those out anyway. Here's another good link:
http://generalspecia...n-checklist.asp

One last thing, try and bring a laptop and pull a rough key right there. It'll tell you a lot about how your results are before you go home. Do it after the first shot. If you have access to a live keyer, all the better. I had one really dirty setup where I wound up using this iphone app that pulls keys. I think if you search for greenscreen in the app store it shows up. Not perfect but it gives me an idea of where the lighting may be off. You simply snap a photo and touch the green to key out and select a background. I had loaded a still of the background on my phone for reference and angles.
Please feel free to ask if you have any questions at all!
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Metropolis Post

Wooden Camera

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