Green Screen Tutorial: Part Two - Using Keylight

Following on from the last tutorial I had on using a green screen, Matt showed us how to edit the footage we had gathered using Keylight in After Effects. The process was surprisingly easy if you were familiar with masks and how they worked and I found that I was able to complete the task very quickly so I asked Matt how to include shadows once I was done with the primary task.

After importing the image sequence, setting up for using chroma key was as easy as dragging the Keylight effect onto the composition and working on from there. To start with we masked around the object to eliminate the screen, however, there was still areas of the screen that were visible.

Masking

Selecting Screen Matte

To solve this, I adjusted the view of Keylight from final result to 'screen matte'. This allowed me to look at my composition in black and white. This allowed me to see where the mask was effecting and where it wasn't and it was easier for me to adjust the curves of the composition to expand the reach of the mask and cover as much of the background as possible. 

Adjusting Screen Matte using Curves

Result of adjusting screen matte

Result

From here I was able to mask out the background and replace it with my own. However, I had chosen a background with clouds, so I went and added a further mask, which I set to 'subtract', so that section of my object would allow clouds to show through to make it fit in with the background more. 

Second Mask

Overall, I found this session very useful and I am confident that I would be able to use a green screen in my work if I needed to and edit it properly. I also found the task quite fun and I would like to be able to use a green screen at some point in the future. 

As I had finished before everyone else and still had time to ask Matt things, I asked him how I would go about adding shadows to the fins of the windmill as it was turning. He suggested that it would be best to add another mask that would create the shadow (using curves for the correct colour/ shading) and use the feathering tool to soften the edges of that mask. 

Creating shadow

Whilst I found this extremely useful to know, I didn't bother animating the mask, as I didn't feel it was necessary for a test, but I do know how to do it and I will use it if the situation ever arises.