The green screen effect

Discussion in 'Amateur Video Production' started by Brian, Sep 21, 2009.

  1. Brian

    Brian Guest

    I've been experimenting with special effects using a small green
    screen made of pieces of green cardboard joined together.
    I would like to have a green screen that covered me from head to foot
    but I don't have a wall painted green. I was thinking of filming
    myself against a wall then using a video effect have the wall behind
    me turn green then I'd compile it as a computer file and reload it
    into Adobe Premiere elements so it appears that I'm standing against a
    green wall.
    Would this work and is there a way of making the background green
    using a video filter in Adobe Premiere elements 7?

    One of the things I'm hoping to do is to suspend an object in the air.

    Regards Brian
     
    Brian, Sep 21, 2009
    #1
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  2. "Brian" wrote ...
    The whole point of using chroma-key (blue-screen or green-screen)
    is that the selected color forms the alpha layer (which you asked about
    last week). If you have some OTHER method of identifying which
    parts of the frame are the wall behind you, (for example, "luma-key"
    if the wall is bright white, etc.) then just go for it and key in whatever
    you want "behind" yourself. There is no point turning it green (or blue
    or any other color). The green (or blue) color is the *method* of
    cutting out the background ("keying"), not the the *result*.
    If you have a method of determining what parts of the frame should be
    green, then you are already have your alpha key and and don't need
    green for anything.
    Once you have an alpha channel "key" (by whatever method) you are
    at the next step where you can insert an arbitrary background.

    It is traditional to use blue or green because those colors rarely occur
    in the foreground subject. Of course, when using chroma-key, ANY
    part of the frame that is the key color becomes transparent. So you
    wouldn't want to wear a green shirt when shooting green-screen, etc.
     
    Richard Crowley, Sep 21, 2009
    #2
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  3. Brian

    Brian Guest

    Hi Ken, I like your idea but if the person has black hair or dark
    shadows would'nt this also be invisible? It would work however if you
    have strong light shining on smoke at night and superimpose this with
    an object.

    Regards Brian
     
    Brian, Sep 22, 2009
    #3
  4. Brian

    Brian Guest

    I thought of that thanks but I want to drink from a cup and put down
    the cup so it's looks like it's supended in the air.

    Adobe Preimere elements has a useful special effect called motion that
    allows you to move objects around and resize them which would work
    like you suggested.

    Regards Brian
     
    Brian, Sep 22, 2009
    #4
  5. Brian

    Brian Guest

    Hi Richard.
    So I need to pick a single coloured background with a rare colour or
    make sure that I'm not wearing the same colour.

    I'm hoping to improve at doing special effects and if I get good at it
    I should be able to make it difficult for anyone to work out how I did
    the special effect such as shaking hands with myself or handing myself
    an object.

    I've seen many amateur short movies but rarely do they 'wow' the
    audience with a special effect as they think it's too difficult to do.
    Regards Brian
     
    Brian, Sep 22, 2009
    #5
  6. Brian

    ushere Guest

    that's why it cost's $mills to WOW the audience ;-)

    as you've observed, most amateur attempts fail miserably. better to tell
    a good story WITHOUT fx than belittle your credibility with shonky,
    second-rate efforts
     
    ushere, Sep 22, 2009
    #6
  7. "Brian" wrote ...
    "Rare" is a relative term. The optimum key color is typically the
    least likely to occur in the foreground objects.

    Because of the way video is typically encoded, green has much
    higher resolution than blue or red, so green typically gives better
    results with amateur video cameras, etc.
    They're right. It IS difficult to do seamlessly. You'll find out yourself.
     
    Richard Crowley, Sep 22, 2009
    #7
  8. Brian

    Brian Guest

    Thanks Ken for your suggestions.
    What I mean by "and superimpose this with an object" is using the
    smoke effect to give the impression that something is burning such as
    a fire in a room or in a car. I'm not certain is the smoke would
    appear in front or befind a person.

    I did some quick shots with a green screen using a still photo camera
    set for video mode so I can quickly get some video clips to load onto
    my computer. I'd use a videocamera once I know what I need to do to
    make this effect work. I'm pleased that there are plenty of video
    effects in Adobe Premiere Elements to make things possible. The motion
    video effect is a powerful tool in this video editor.

    Regards Briam
     
    Brian, Sep 22, 2009
    #8
  9. Brian

    Brian Guest

    It seems to be the timing that's difficult and having myself or
    objects in the same position between shots. I recently did a simple
    effect where I'm talking to myself as two Brians appear in the movie
    clip and it was the timing I had more trouble with. I'm pleased that
    Adobe Premiere elements has the tools to make it possible to create
    special effects in a video. Moving an object around the screen is
    simple to do using the 'motion' video filter with keyframes.

    Regards Brian
     
    Brian, Sep 22, 2009
    #9
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