This week Pete wanted to introduce us to chroma keying to expand on our VFX skills.

“Chroma key compositing, or chroma keying, is a visual effects/post-production technique for compositing (layering) two images or video streams together based on colour hues (chroma range).”

First, I had to import the footage into a new composition in Adobe After Effects. We had 2 files to work with; the Depth of Field (DOF) file and the Backplate.

For the Backplate, I changed the track matte to luma matte and I made it a parent to the DOF. For the DOF, I changed the blending mode to Hue.


With these changes, I then created a pre-composition with the two, edited files; named BACKPLATE. I applied a Gaussian blur (with a value of 3) to BACKPLATE and edited the curves (brightness) to make the footage look more natural and realistic.


Next, I added chroma key to the composition and applied the Keylight plugin to it. On the plugin, I used the eyedropper tool on the screen colour to select the part of the green screen that’s closest to the woman. This removed the majority of the green screen, however there were small marks on the screen that I had to get rid of.

I went into Screen Matte view and changed the clip black value to 25 and the clip white value to 60. This allowed me to get rid of the marks.


To make her blend in more, I had to edit the edges of the chroma key so that they weren’t so sharp. I changed the screen shrink/grow value to -0.8 and the screen softness to 0.6. I also enabled edge colour and set the brightness value to -18.


The final step to make the woman fit into the scene, was that I edited the brightness curves on the layer and I set the saturation value to -41 as the was very bright and colourful against the pale background.


Finally, I had to add masks to get rid of the equipment on the chroma key footage. I started by using the pen tool and drew around the equipment on either side of the footage and I made sure not to cover up the woman. Then I created a mask that surrounded the woman which was easy enough but when the gun passes over equipment, I had to edit the mask frame by frame. I changed the woman’s mask type to add and everything around her disappeared.


After the masks were used, I had finally succeeded at inserting chroma key footage onto a backplate and making the woman look like she is actually there.

Overall, I am happy with how this experimentation turned out and I’m excited to work with chroma key in the future. If I were to work on this further, I would probably add gun shot effects and insert enemies that the woman is shooting at.


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