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Thread: Green Screen - What are the best settings?

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    Default Green Screen - What are the best settings?

    About to shoot my first green screen sequences with the HV30.

    Is it best to shoot in DV or HDV and what are the best settings for shooting green screen on this camera?

    Thx

    Kevin

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    Legend lordtangent's Avatar
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    The most important this is to make sure your screen is properly set up and as evenly lit as possible. If the screen isn't lit evenly you can forget about ever getting a good key. This one aspect is more important than any camera setting.

    You should place your subject as far from the screen as possible while still getting the coverage you need. Placing the subject away from the screen will reduce the visibility of spill from the screen and preclude the possibility of the subject casting shadows on the screen. Remember that you can always garbage matte out stuff on the very edges of frame. The goal is to get a good edge matte for the moving subject.

    Also, it's usually easier to pull a key from progressive footage. So, settign your camera to the progressive mode is probably the only "setting" other than locking exposure that is really important.

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    Senior Member ncusa367's Avatar
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    Quote Originally Posted by Federated Films View Post
    Is it best to shoot in DV or HDV and what are the best settings for shooting green screen on this camera?
    HDV all the way, you want lots of pixels to work with.

    If you have lots of movement, you may want a higher shutter speed so that you won't have blurry edges around the subject

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    Can you set Progressive mode for just DV?

    I find the index in the manual awful, it doesn't list Progressive or Zebra, two functions I'm looking for at the moment!

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    I forgot to mention... One trick for lighting the screen evenly is to use the zebra stripes in the camera. Point the camera at your green screen and set exposure so the zebra stripes just start to light up on the brightest parts of the screen. Adjust the lights until the zebra strips are even. You can adjust the exposure up and down to confirm the stripes (hence the light on the screen) is are even over the entire green screen.

    The green screen should be a normal exposure. That is to say it should not be over or under exposed relative to the foreground subject. A lot of people agree that one stop under 70 IRE is the correct exposure for the screen. I haven't tested enough with the HV20 to know if that holds true on the HV20, but it should be a good starting place. It is convenient since the HV20 has a zebra stripe at 70 IRE setting, which will make setting that exposure easier.

    And yes, you should shoot HDV even if your target is SD video. The extra resolution will help you get a better key on fine details like fly-away hairs, etc.

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    Legend lordtangent's Avatar
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    Quote Originally Posted by ncusa367 View Post
    If you have lots of movement, you may want a higher shutter speed so that you won't have blurry edges around the subject
    If you've lit the screen correctly and use decent keying software you can get a good matte even from motion-blurred stuff.
    Last edited by lordtangent; 2009 April 14th at 16:50.

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    Great tips, thanks.

    It just interviews so nothing too exciting.

    BTW Do you know if you can key in iMovie 8 or do you need to use a more pro programme like FCP ?

    Kevin

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    Default One other thing...

    Perhaps because it seem like a no-brainer, but I see people forget it all the time. No auto white balance. Manually balance to the foreground lights only, keeping the green completely out of frame (or with the lights illuminating it turned off, if possible,) and lock. Otherwise you'll not only end up with some hellacious skin tones, but also a contaminated green (blue, etc.) as the camera attempts to compensate. And needless to say, another seeming no brainer... lock your exposure or, again, your color values may change, making the best key harder to pull.

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    Senior Member Atnas's Avatar
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    Great tips in this thread. Definitely learned something. I do however still wonder what to do when I want a shot of the whole person. How do I place the lights to get the least shadows?

    And Matt.
    I never thought of those no brainers

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    Quote Originally Posted by lordtangent View Post
    I forgot to mention... One trick for lighting the screen evenly is to use the zebra stripes in the camera. Point the camera at your green screen and set exposure so the zebra stripes just start to light up on the brightest parts of the screen. Adjust the lights until the zebra strips are even. You can adjust the exposure up and down to confirm the stripes (hence the light on the screen) is are even over the entire green screen.

    The green screen should be a normal exposure. That is to say it should not be over or under exposed relative to the foreground subject. A lot of people agree that one stop under 70 IRE is the correct exposure for the screen. I haven't tested enough with the HV20 to know if that holds true on the HV20, but it should be a good starting place. It is convenient since the HV20 has a zebra stripe at 70 IRE setting, which will make setting that exposure easier.

    And yes, you should shoot HDV even if your target is SD video. The extra resolution will help you get a better key on fine details like fly-away hairs, etc.
    This is the kind of stuff they SHOULD be teaching in schools/colleges.
    Thanks for the tips.
    In the UK? Then post here. You might need a hand in the future from a real person... HV20 (PAL)

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    Senior Member DebG.'s Avatar
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    Quote Originally Posted by Federated Films View Post
    Great tips, thanks.

    It just interviews so nothing too exciting.

    BTW Do you know if you can key in iMovie 8 or do you need to use a more pro programme like FCP ?

    Kevin

    Not iMovie 08, but iMovie 09 has a new green screen feature. Haven't tried it yet myself, though.

    Deborah
    HV30, HV40, Rode VideoMic, Juiced Link , FCPX- http://www.MakingASceneProductions.com

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    Quote Originally Posted by Atnas View Post
    Great tips in this thread. Definitely learned something. I do however still wonder what to do when I want a shot of the whole person. How do I place the lights to get the least shadows?
    I'm assuming you're talking about shadows around the feet, as anything behind can be eliminated just by keeping the screen back far enough to fill them with the background lights... ideally you should gel those lights with a green/blue that matches your screen and use barndoors or flgs to keep them off the foreground subject. A more old school approach is to have the actors stand on a reflective material like mylar... no shadows that way, though you'll have to roto out the actor's reflection. A newer variation is to use front projection screen material and a colored ring light.

    A simpler approach is not to worry about it and fix the whole thing in post with a garbage mattes and roto... although you may not even have to do that.
    I use the old Ultra 2, which is a vector keyer rather than a chroma keyer, and it's never had a problem with getting rid of shadows... it even generates synthetic shadows to replace the real ones. Unfortunately, Ultra hasn't been available separately since Adobe bought it from Serious Magic and made it part of the uber-CS3 package, and it completely disappeared from CS4.

    If the camera's locked off or you've placed motion tracking markers on the screen, one simple trick is to shoot a clean shot of the screen. Pull a key from the SHADOWs and depending on your workflow, then either key the original green screen in over the main footage or combine the mattes together.

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    Senior Member Atnas's Avatar
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    Thanks for the info, will probaly do some more rotoing then
    Quote Originally Posted by Matt Greenfield View Post
    A newer variation is to use front projection screen material and a colored ring light.
    Cool, havn't thought of that. Sounds too expensive for me though.
    Quote Originally Posted by Matt Greenfield View Post
    If the camera's locked off or you've placed motion tracking markers on the screen, one simple trick is to shoot a clean shot of the screen. Pull a key from the SHADOWs and depending on your workflow, then either key the original green screen in over the main footage or combine the mattes together.
    Could you explain this in depth? Wasn't able to follow you. Do I key out the green in the clean shot, leaving only shadows? And then I do what with it?

    I'm using AE CS4 + Keylight for keying, and from what I've read, it should be better than Ultra, but slower.

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    Quote Originally Posted by Atnas View Post
    Could you explain this in depth? Wasn't able to follow you. Do I key out the green in the clean shot, leaving only shadows?
    Sorry if that wasn't clear. First, don't worry about the clean plate so much.... that's more for Ultra, which can pull a key off a stucco wall or badly wrinkled backdrop if it has a photo reference. If you're only chroma keying, you don't absolutely need the clean shot to pull from; it'll just take a few more steps:

    The trick to remember that is that a keyer really doesn't care what color it's keying, as long as it's within a certain range. So, rather than trying to pull your key in a single pass off your master shot (the one with the actor,) you instead pull your matte in several passes and add them together. To get the best key off the hair, etc, do a very tight (colorwise) key off the backdrop behind the head. That'll probably leave you a pretty good overall but with with some garbage where shadows are on the screen. To fill those, you go back and pull a second key, this time sampling your key color from the shadows cast on the greenscreen. Presto, you've now got a new key (alpha matte, whatever nomenclature you prefer) that should be close to the shape as your shadows. You may have to do several passes sampling different areas of the shadows to completely fill the holes, but if you've got shadows moving behind the actors body it's generally easier than trying to articulate a matte.

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    Thanks matt

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    Quote Originally Posted by Atnas View Post
    Great tips in this thread. Definitely learned something. I do however still wonder what to do when I want a shot of the whole person. How do I place the lights to get the least shadows?
    I'm assuming you want to see the peoples feet, correct? If the camera is going to be locked off there are a couple of things you can do. Some of it depends on what keying software you are using. For example, Ultimatte has a feature that allows you use a clean plate pass to differentiate between shadows and foreground. So basically you can key both shadows and foreground. Ultimatte removes the green from the shadows and adjusts their transparency proportional to their density. So, in the case of ultimate, you can use a "cove" or "cyclorama" type screen with green under the actors feet and not worry too much about the shadows.

    If you don't want to see that shadows at all, you can use mylar or a plastic mirror for the floor under the actor. That way the screen behind them is reflected in the mirror and you can pull a key off it.

    You can also use a combination of "difference key" and roto to cut the feet out.

    However, when it comes to keying, there is no single formula that works all the time. The foundation of a GOOD key is a properly lit and exposed screen. But after than it's not uncommon to use a lot of procedural keying tricks to get a good quality matte (not just what comes right out of the keying software) and roto. Sometimes you need to use multiple keys, each for different parts of the body (the hair in particular) and combine those with other parts using garbage mattes and/or roto.

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    Quote Originally Posted by lordtangent View Post
    However, when it comes to keying, there is no single formula that works all the time.
    Word. The subject could fill an entire book just by itself. In fact, it did. This one:

    [ame="http://www.amazon.com/Greenscreen-Made-Easy-Compositing-Techniques/dp/1932907548"]Amazon.com: Greenscreen Made Easy: Keying and Compositing Techniques for Indie Filmmakers: Jeremy Hanke, Michele Yamazaki: Books[/ame]


    And it's not a bad book book at all from a technical perspective, although some of their history is a little wonky or just plain wrong. But hey, if you-a wanted-a to learn history, you could-a go to film-school, right?

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    I'd use a light meter to take measurements in the four corners and the center. Anybody else?

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    Default Additional Greenscreen resources

    Pro Video Coalition's Greenscreen Primer (Pt. 1)

    The people behind the Hollywood Camerawork DVD series are coming out with a new set called Visual Effects for Directors. The promo page includes several free video lessons on greenscreen technique.

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    Wow, now this is a post worthy of a sticky.

    I'm watching one of the green screen videos on that site you linked to,
    and it's like nothing I've ever seen, - very in-depth info that is just amazing.

    Thanks for posting this Erik !

    Dave


    Quote Originally Posted by Erik Bien View Post
    Pro Video Coalition's Greenscreen Primer (Pt. 1)

    The people behind the Hollywood Camerawork DVD series are coming out with a new set called Visual Effects for Directors. The promo page includes several free video lessons on greenscreen technique.

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    Supergood material to learn from for everyone that edits footage on the PC(effects and such, not only editing):

    http://www.hollywoodcamerawork.us/vf....php?src=front
    http://www.hollywoodcamerawork.us/vf....php?src=front
    http://www.hollywoodcamerawork.us/vf....php?src=front
    http://www.hollywoodcamerawork.us/vf....php?src=front
    http://www.hollywoodcamerawork.us/vf....php?src=front


    Very helpful, seriously interesting and educational top notch stuff
    Blazing hot. www.xgbeatz.com

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    I take it you work for them, however, posting the SAME link 5 times is a bit over the top, you don't think ?

    Quote Originally Posted by ReLogic Studios View Post
    Supergood material to learn from for everyone that edits footage on the PC(effects and such, not only editing):

    http://www.hollywoodcamerawork.us/vf....php?src=front
    http://www.hollywoodcamerawork.us/vf....php?src=front
    http://www.hollywoodcamerawork.us/vf....php?src=front
    http://www.hollywoodcamerawork.us/vf....php?src=front
    http://www.hollywoodcamerawork.us/vf....php?src=front


    Very helpful, seriously interesting and educational top notch stuff

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    Once you have your screen setup you can drop the exposure on your camera and watch the viewfinder. The screen should fade/darken evenly as you change the exposure. If not, adjust your lighting. Quick and dirty, but it works.

    A hair light along with back lighting the talent will make the keying easier if the screens not lit exactly right.

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    No I'm not working for them, if just had to mention that their DVD series is very helpful and informative.
    Blazing hot. www.xgbeatz.com

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