Green Screen, Tracking & Compositing

The green screen, motion tracking and compositing masterclass was a very unique experience in that it gave us an opportunity to work with respected industry professionals, DOP Nick Paton and editor and owner of the Post Lounge, Steve Cooper. Our task for the day was to create two moving shots- one with the camera tracking across the set and the other with the camera dollying into the window- of the set with a green screen outside of the window. The second half of this, was to shoot some static footage of an outdoors environment. So, we commenced the day by designing the set, carefully placing props in the space with focus on one particular vase which sat on a table directly in front of the window. The next thing we did was place roughly 6-9 tracking markers (two small trips of black tape crossed over to form an “X”) in the shape of triangles on the green screen and three on the vase. One of the greatest things about having Steve and Nick with us for the day was that they really wanted to make sure that we all knew what was happening and why.

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Being a post student who has done very little work with green screens, the highlight for me was having Steve take the time to not only explain the green screen and tracking process but to show us (especially the posties). Being that there are only two post production students in our class, he had us placing and moving the trackers, checking through their positions through the split monitor and guiding us to fix them as required. This was a really great feeling to have someone like Steve show interest in teaching us new skills. From this, I learned that the purpose of tracking markers is to provide extra information for editors and post-production software to create an effective image replacement. In our case, we would be replacing the green screen with the footage shot of the outside environment. In the edit, these trackers are used to more precisely key out the green screen and identify/ match the appropriate distances to create a realistic finish.

While on set, there were some technical elements that were taken into consideration to assist in achieving this sense of realism. These included the height of the camera from the ground, the angle at which it was sitting and the distance between the camera and the vase. Additional considerations were made for the direction of the lighting in order to emulate the natural light that would come through a window. These details are significant to note as together they provide the foundation for a seamless integration and edit between the plate shot and the set footage.

In terms of filming, the hardest part on the day was trying to get the lighting right, however having Nick on set really helped to speed up the process and fine tune things like reflections. The edit for this project was definitely the most challenging and involved process.  I wouldn’t day that this post work difficult as such, it was more so just how time consuming and fiddley the steps were that made it challenging. Being a post student, I had two tasks to complete using the footage. The first one, being the same as the production students, was the replacement of the green screen with the plate shot in the sideways track. The second was to replace the background and the vase on the dolly into the window. With post production facilitator Alex Adam, we stepped through the keying processes. I found the first edit to be much more manageable than the second, the reason being that I had to learn new software in order to replace the vase with the provide 3D gnome. This software was called Cinema 4D and I had never used, or even heard of it before. However, after having a bit of a play, I was able to get the hang of it and could relate some aspects of it to another program that I’ve used in the past for an animation class called MAX 3D.

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The other program we used for this project, actually the main one, was Adobe After Effects. One of the good things about these software is that they can be used in conjunction with each other through dynamic linking. This makes the flicking back a forth a little less ‘clunky’. For this particular 3D task, the process went as follows: We imported the required footage into After Effects then added a 3D camera track to the shot of the set with the green screen. Following this, we applied a couple of solid layers to the objects in the room to help with the placement of the, soon to be added, Cinema 4D layer. After making a few sizing and positioning adjustments to the gnome, we added Keylight on the base footage.

It took a bit of fine tuning to get the scend running smoothly with the gnome, but I did get there. To finish it off, we went back to the footage in After Effects we went through and masked out all on the black trackers on the green screen. This was a small and easy fix. Finally, to tidy up the gnome, we went back into Cinema 4D to change to direction at which the light was hitting the statue to match the light of the scene. Last but not least, we used Photoshop to remove any red spill and leftover glimpses from the original vase.

Overall, it was a great masterclass whereby I learnt a new program, was taught some things I previously didn’t know and was able to practice my compositing skills.

 

 

 

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