Monday, April 25, 2011

Green With Envy: Using Chroma Key

Last year at the Upstate Technology Conference I had the pleasure of hearing the keynote from Hall Davidson of Discovery Education. One of the tools he mentioned was the chroma key feature found in video editing software. Most people are probably familiar with the "green screen" effect during the weather reports on news broadcasts and special effects for high budget films. Well, it doesn't take much money or technical ability to create this effect with your students. I knew that our students would love doing this and it was definitely something new to them, but I didn't try this until today.
A big thanks to the Mighty Little Librarian and her post "I'm A Green Screen Machine" because she reminded me of this tool and prompted me to give it a try. I was pleased to find that the software I wanted to use was free and not blocked. I used Jaycut, although there are other options out there. I purchased a bright green curtain from Walmart and pulled out one of our Flip cameras. With a little nudge my library helpers agreed to star in the video. I downloaded a few video clips from Discovery Education's United Streaming and wrote a very short script explaining the tool and how I could help teachers implement it in class. While I manned the book fair my student helpers recorded the video then I did the editing. I was pleased to find it very easy to do.
In Jaycut you need to upload the video clips first. Drag the green screen video to the Video A row and the other clips to the Video B row. I trimmed the Discovery Education videos to correspond with the script and moved them around where I wanted them. If you are familiar with MovieMaker you will find this software to be easy. To enable the Chroma Key effect, double click the green screen video clip, choose the Effects Tab, click Yes for Chroma Key, ensure the color selected matches your screen (green in my case, but it can be other colors), and adjust the sensitivity. I set the sensitivity to 40%. I really wanted to increase it to hide a wrinkle in the green curtain, but when I did it erased my student's white shirt and blond hair. Just play with this until you get it where you want it. I learned to make sure there are no major wrinkles in the curtain before you record. I also suggest having lots of green in the shot so that viewers can see the clips. In my case the only way they agreed to do the talking was together so you can't see much of the background.
I used video clips as a background and I did not want the audio. To remove the audio, double click the clips in Video B, select the Audio tab, reduce volume to 0%. You could use the audio if you wanted to mesh the clips with the audio from your students by trimming the clips and adjusting audio for each clip. You can also use an image as a background and then audio would not be a concern.
Please don't judge my video too harshly. It was a learning experience, but I had fun creating this little video and can't wait to try this with our students. Two teachers have already expressed interest in using this for a project. One of our science teachers plans to try this soon and one of our English teachers wants to use it to create book trailers.
Have you tried chroma key? What ideas do you have for using this in the classroom or library?

Green Screen Demo


  1. YAY! So fun :)
    I created a similar video and showed it at a faculty meeting to drum up some business. Your teachers and students are going to LOVE it!!

    Last week, our journalism club went on a field trip to the news station. A teacher came back and told me the students were talking to the weather people about chroma key, which they learned about in the library!


  2. Awesome job, Tamara!

    I'm sure you'll get some "bites" from your teachers. If not, if you show it to more of your students, I bet they'll want to do one for a project instead of the old boring ppt or poster. Have them ask their teacher to allow them to substitute one of these as their project.

  3. Chroma key feature sounds really cool for video editing.
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