Green Screen/Chroma Key

Today I learnt the basics of green screening or chroma key. I went to a room with a reflective sheet covering the wall. There then was a green light on the camera to project the green onto the sheet. This is a great technique to create all sorts of special effects within film and television. This also can be used within the gaming industry for cutscene special effects.

We then recorded some footage of someone in front of the green screen doing some actions to later put onto the computer and work with.

The fist step is to import the clip into After Effects, then to drag onto a new composition. it should look like this.

Screen Shot 2016-02-01 at 11.57.39

Screen Shot 2016-02-01 at 12.17.56.png

After adding the video clip you need to select it and add an effect called Keylight. This will give you all the options to change the background to whatever you like.

Screen Shot 2016-02-01 at 12.02.44

This gives you a number of settings to change to adjust the background colour. The first step is to use the key colour tool to select the background colour. After selecting it it should look something like this.

Screen Shot 2016-02-01 at 12.22.04.png

Its a good start but it isn’t quite what we are looking for, so to improve the transparency of the back ground you can adjust the settings in the on the left to get a level of colour you want. To help you see the difference better you can go on view and change the setting to Screen Matte.

Screen Shot 2016-02-01 at 12.26.50

Screen Shot 2016-02-01 at 12.26.39

This really helps to see the difference between the person and the background. The idea is to get the background as black as possible and the person as white as possible.

After tweaking the settings for a while, which ended up look like this for me, but every image will need to be adjusted differently.

Screen Shot 2016-02-01 at 12.02.55

After doing the final touches i added a box around the actor to crop out some background i couldn’t get rid off via settings and this is the final product i ended up with.

Screen Shot 2016-02-01 at 12.03.31

As you can see the back ground is completely invisible and now the clip is ready to be put in front of any background the user may want to as well as any special effects they may want to use.





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