Behind the Green Screen Part II

Our early green screen efforts were less than desired and never made it into our finalized productions. While we were able to remove the overall green screen background in PowerDirector 9, we were left with a green halo around the actor and a hazy mostly-transparent background.  You can read more about that in Part I of this series. 

PowerDirector was unable to fully remove artifacts from our green screen clips.  We followed these tips for using the green screen and reshot:

-          Stand a couple feet forward of the green screen.  That will reduce shadows.

-          Include backlighting. Any remaining shadows are eliminated.

-          Stretch out wrinkles in the fabric.

-          Light as evenly as possible.  Editing software will have an easier time keying out the green screen.

-          Don’t wear anything green.  Sounds simple enough, but we had some greenish zombie makeup in one of the clips which was enough to make a cheek transparent.

-          Only move where the camera sees you in front of the green screen.  Again, this sounds simple and it is when you’re sitting down, but it’s more difficult to manage when you’re swinging toy light sabers around.

-          Don’t wear anything reflective.  A white shirt is more likely to reflect a green light. Sanj’s beanie has blue plastic propellers, the underside of which tends to pick up and reflect green light. If you need to shoot something green use another background color. Blue, black and white are commonly available.

Here’s the list of goods used in our makeshift basement studio:

Cowboystudio 4 Piece Continuous Photography /Video Studio Digital Lighting Kit with Umbrellas and Background Lights

$70.93

SP2000 Backdrop Background Support Stand For Muslins, Scenic Backdrops and Chromakey Greenscreens or Bluescreens

$69.95

Prism Backdrops 10X20′ Chromakey Green Muslin Photo Video Backdrop Background

$45.69

3.75″ Muslin Clamps, Pack of 6

$7.95

Total

$194.52 (not including tax or shipping)

Basement Light Studio

Lights, Camera, Action!

Despite the effort, PowerDirector still left us in a green halo.  PowerDirector may be fine for trimming and editing home movies, but it was clearly inadequate for what we were trying to accomplish.

After some research, we arrived at Adobe After Effects CS 5.5. It does a much better job at removing the green screen halo and background digital fog.  There’s a Keylight 1.2 effect that does a fantastic job of removing the background.  We used it extensively in our Dear Zombies series, especially in Episode Two where we replaced the background of each clip with a photo.

The clips were filmed in my basement.

Basement studio

Dear Zombies Hot Seat

The Keylight 1.2 effect from The Foundry, available in After Effects, did a respectable job with default settings.  With a little tweaking, the results are even better. The following steps take you through the same approach we followed and assume some familiarity with After Effects.

  1. Launch After Effects. Add a video you’ve previously recorded using a green screen to a blank project.
  2. Create a new composition and add the clip you just imported to the composition. For reference, here’s a sample clip I’m currently editing. It already has a mask applied which is a subjection of another discussion.
    Sample original clip
  3. Select Effects -> Keying -> Keylight 1.2
  4. Click the eyedropper and select the most prevalent shade of green. This will eliminate most of the background, but some artifacts may remain.
    Keylight Selection
  5. To view the artifacts, change the selection in the View drop down from Final Result to Combined Matt.
    Hazy edited image.
  6. There’s some haze in the dark areas and some black shadows in the white. This will muddy the background you add later. To eliminated that, expand the Screen Matt option and adjust the Clip Black and Clip White options.
    Adjusted clip settings
  7.  Adjust these settings until you have a solid black background and a solid white foreground.
    cleaned up matte
  8. Select Final Result and you’re ready to proceed with inserting a new background.
    Final Image

We found that the green screen we were using was adequate for our Dear Zombies responses and to capture a single, standing person, but once you have two people moving around there are issues.  In the image above, there are some artifacts just behind the zombie on the right that still need to be cleaned up. More on that in next week’s installment.

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One Response to Behind the Green Screen Part II

  1. Jacki says:

    Kick the tires and light the fires, prboelm officially solved!

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