My first pass was to key and garbage matte each shot. I kept this relatively simple to start but found that most of my footage worked better with multiple keys.
I've found Keylight and Ultimatte to give the best results on this particular footage.
Keylight is picking up hair detail better in many of the shots but giving a dirty alpha, while Ultimatte is nice an clean but also chops off the detail.
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| Ultimatte Key- See the lack of detail in the hair |
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| Keylight Key- Nice detail but.... |
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| ... the best Alpha I could get from Keylight without losing detail |
The solution? Use them both! I added a key mix to this shot and rotoscoped a basic mask to determine the area each key effected.
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| Key mix set up |
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| Final Alpha |
Working with Problem Shots:
For one shot I plan to composite two shots together. One actor starts in front of the greenscreen but runs off it so I have a roto job here, while the other actor stays in front of the green screen. Unfortunately the second actor is, once again, out of focus so this shot might take longer than I thought!
In an attempt to cut down on rotoscoping I experimented with the IBK (image based keyer) node. IBK is made up of two parts- IBK colour and IBK gizmo. IBK colour is used to generate a cleanplate while IBK gizmo uses the cleanplate and footage to create a key. I already had a clean plate for this shot so I used my own.
Unfortunately the results weren't great. The ares where the actor went off the greenscreen did key out but the final key was really messy. I couldn't think of a way to fix it other than rotoscoping anyway so I decided to scrap this and just get on with the roto!
Another of my shots involves compositing 3 actors into the same shot. The last part should be simple, all three actors are in front of the green screen and the camera has the same settings and placement; but I knew I would have a roto job on my hands for the first half of the scene.
Unfortunately things are more complicated than I originally thought. Turns out that the focus on each plate isn't as sharp as it could be- which gives a beautiful green or yellow glow to each actor.
This is also a problem sometimes on motion blur as well so I've found a tutorial that gives a handy node set up for reducing spill.
how to despill a greenscreen shot - same approach in smoke and nuke from torsten neuendorf on Vimeo.
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| Original footage |
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| Despill node set up and Rotoscoping in action |
Since the action in this shot also goes off the greenscreen a significant amount of rotoscoping was also needed.
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| A closer look at the Rotoscoping required in this shot |
Nice - great visual evidence. Thanks, Sarah!
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