Of Greenscreens

I learned how to green screen!

For our module in Introduction to Filmmaking, we were asked to edit our short dialogue scene we shot during the all day exercise with green screen and to key a background into it in Avid Media Composer 8.

So after I finished the rough cut and a short introduction by our technician, I was able to add a new video track onto the timeline, choose a background picture and add the relevant effect onto the clip.

For this, I opened the video effects panel from my master bin, selected Key from the dropdown menu and selected Spectra Matte to drag onto the relevant clip with the green screen.

After that, I selected the Effect Mode tile left from the timeline and picked an average green tone from the background to give the effect a base to key against.

I then searched for a fitting background image with the same resolution as the film. This turned out to be a more difficult task than I previously imagined, since I did not find a satisfying background that was not slightly angled, tilted or otherwise distorted in perspective. After 20 minutes, I decided to pick the best compromise I could find, downloaded and linked it to my project bin.

I then added a new video track and dragged the image into it, which gave me 30 seconds of default material to work with. After activating the track, the effect applied to the background and I had successfully keyed the background.

Or so I thought.

Turns out that filming with green screen needs you to keep an exact eye on shadows on the green screen. While I tried to eliminate them as much as possible during filming, there were still slight remnants that were not visible on the display before.

Now they were. I know because on these parts of the image, the background turned grainy and pixelated when playing the clip. Also, I suddenly saw a lot of green splash on and around the actors, which was now also keyed to the new background.

So I tried to eliminate that visual noise by adding the effect twice to the clip and thereby picking a darker green tone. The noise did not really change or at least I could not discern it.

I then experimented with the controls on the effect panel, trying to bring about a change in the image. With this particular clip, I later found out that setting the inner saturation to 60 and the outer saturation down to 0 somewhat weakened the noise to a more bearable degree.

After having visually denoised my footage to the best of my current abilities, I exported it. Which, in the first attempt, just gave me a couple of seconds of the whole material.

What had happened?

Without noticing, I accidentally set in- and out-points on the timeline, which reduced the area of the clips to be exported on that minimum. So I instead placed the in-point to the beginning and the end-point to the end of the clip and exported anew.

This time, it worked:

References:

Svea Hartle (2017) A Good One (2nd Attempt) [online]