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Flawless blue screen compositing


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#1 Niki Mundo

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Posted 13 September 2006 - 05:16 PM

Hi, I'm new to this board. My major question i've been wrestling with for some time is I would like to film a feature technically Sin City and Sky Captian.. using a 100% green screening system. The only differance is that I would like to use real footage (like exterior street) and then place actors from a studio set onto that footage. Nothing CGI or animated

Now- I know this can be done basically, but I hate the "fake" look alot of traveling mattes I've seen in the past.

Is there software that would help make it more seemless? I don't want the audience to know what I've done.

Also what about shooting the source material on super8 then film the green screen stuff on 16mm, or
16mm source with 35mm green screened actors? What about video? Anything to make it realistic..

Thanks for any help, you guys would know.

Edited by Niki Mundo, 13 September 2006 - 05:17 PM.

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#2 Patrick McGowan

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Posted 13 September 2006 - 05:25 PM

I'm sorry... let me organize this is my head. You want to take the time to shoot it in front of a green screen, but use a location like a random street and make it look perfectly natural?

I'm not a professional, but my suggestion would be to use the location, where your going to film this "street" b-roll and put the actors there. I think that would look pretty natural.

Sorry, I'm kind of kidding, I think it's great that you are interested in using a green screen. I don't really have any advice though.
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#3 Niki Mundo

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Posted 13 September 2006 - 05:39 PM

Yes the best way would be to have a secure location but as a low budget filmmaker it's not possible.
I don't want to get cop, property owner, tenant - who knows..attention.

I want maximium control and I think technology today allows it.

Like I want to film a scene inside a bank lobby. I go pick up the source material (film the interior), get a little hasseled but I still get the scene later on..
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#4 Niki Mundo

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Posted 13 September 2006 - 05:51 PM

I know Robert Rodriguez shot Sin City entirely on green/blue screen in a werehouse in Austin, TX.
I like that idea alot.
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#5 Phil Rhodes

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Posted 13 September 2006 - 06:55 PM

Hi,

Almost all blue and greenscreen material has manual retouching done, and even then it's spectacularly difficult to make it look completely realistic. It's easy to find big, expensive movies with really horribly bad compositing in them (the first Harry Potter had some rotten stuff).

The ease with which it's possible to get reasonable results is largely due to the type of shot you're trying to do, how much interaction there is between real and composited objects, what the light's like, and how well you shoot the green elements. It's a huge subject, but in short it's easier to do a head and shoulders against a very distant background, locked off, in daylight, than it is to do a complex tracking move with people moving around semi-transparent objects at night.

Shoot some tests.

Phil
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#6 Jaan Shenberger

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Posted 13 September 2006 - 07:24 PM

well-executed, convincing greenscreen composites require A LOT of skilled work... and if the bulk of the work doesn't occur at shooting/lighting then it will have to occur in post, usually in twice the quantity.

i have heard from a compositor that worked on sin city that it was a nightmare job. from what i've heard, there was an absurd amount of rotoscoping needed.

also keep in mind that doing greenscreen composites for a final b/w image is a lot easier than finishing to a color image.

also, the idea of shooting greenscreen actors to match with existing locations is going to be very hard to do because of the difficulty in matching up lighting and the subtle organic color reflectance/bounce generated by the location (the achilles heel of grscr compositing). when the locations are being created via CGI, they can adjust the lighting to match the footage of the actors. also, camera moves and even panning/tilting will add great complications (motion tracking & photogrammetry will be necessary).

but if you do go ahead with it, two things that will save you loads of trouble (and despair) will be to avoid showing the actors' feet touching the floor and to shave their heads or have them wear hats.

not to sound like a downer, but it's almost certainly not worth it unless you yourself are an ace compositor and know how to plan/shoot around the limitations.

Edited by Jaan Shenberger, 13 September 2006 - 07:27 PM.

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#7 Niki Mundo

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Posted 14 September 2006 - 12:46 AM

Thanks for the replies.

What about the combo of 16mm source material and then 35mm green screened elements??
(or Super8 and 16mm)

Would that make a better quality composite? (I care not of grain etc..)
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#8 Phil Rhodes

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Posted 14 September 2006 - 06:25 AM

Hi,

16mm is not a great idea for compositing as the registration can be rather poor; I have never tried it with super 8, but I an only assume it will be considerably worse. It's my impression - having done alot less work with film than video - that film is vastly more difficult to do well due to constantly changing grain.

I think you're asking for a lot of trouble here.

Phil
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#9 Mark Duckworth

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Posted 14 September 2006 - 06:58 AM

Well, I have done a lot of compositing using various programs like Shake, Combustion, Fusion. Usually if I light the greenscreen to what I think is close to perfection, being very very careful and shooting some tests beforehand, I still end up spending more time than I wish using the above mentioned programs to get it to look right ( ie, biggest greenscreen in the world in a mid shot, yet somehow one actors elbow manages to go off the screen). Granted I only do compositing using video and with a 4:2:2 colorspace. However, there are a few websites you can peruse to get a better idea of the challenges, VFXTalk.com is a good one. A general consensus from what I have read, listened, is that a good composite still takes time even with today's technology. I cant imagine what it was like to do before digital compositing, I find my patience now stretched to the limit with computers. Some good tips are shoot using the largest colorspace you can (4:4:4 is the best) try to keep the actors from wearing any colors which share similaries with the screen you are shooting on (Green or Blue) so you can cut down on painting and rotoing in post and light your screen first and then light your actors.
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#10 Jon Kukla

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Posted 14 September 2006 - 02:58 PM

Securing locations with local authorities and finding a good production designer will likely be far easier, I would hazard to guess. But then again, it may be worth at least trying a test to see if you're up for really doing the greenscreen for the full haul.
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#11 Andre LeBlanc

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Posted 14 September 2006 - 03:55 PM

It looks like everyone's given you some great advice. In my own experience, if you're not trying to go for incredibly difficult camera moves, then locking the camera down (not moving it at all) might save you some nightmares. If you're doing anything with pans or tilts or push-ins you're going to complicate your work exponentially by having to track or stabalize the footage... . I find even the smallest micro-movement in a track, or most minor swimming in a green screen key can make everything look very amateur. The simplest you can block off your location plates, the better. If you're doing the work yourself, then you'll want to simplify as much as possible-- unless you're trying to make an fx reel.
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