Film a clean-plate green screen for chroma keying productions

I have a beginner's tip for when you are using Natron as your keyer & compositor for green screen projects.

I will give a brief tip via snapshots. But when you are filming your green screen projects, I recommend that you film a cleanplate of your scene if its a static shot. If you have a budget of motion camera, film a clean plate. Here is why. Natron has a keyer called PIK and PIK Color. PIK node has a C channel input were the PIK Color node connects. The PIK Color node is a specialized node that helps generate a clean plate from single shot with green screen background. That node is beyond this tip and for another tutorial.

Our contributing developers has developed a node called "lp_CleanScreen1". It will allow you to use a filmed cleanplate or solid color node to help with math that give you more control of pulling your key. Plus it makes it easier for those uneven backgrounds to be pulled more evenly.

There are 4 attached images. One is the original setup with me sitting as the talent. Another image of me sitting and only just the Chromakey Node used to pulled the key. You also can see the artifacts in the Alpha channel on the right. 

The 3rd image is of me using the lp_CleanScreen1 and my film cleanplate. You can see that with no black and white levels used to clean up the matte. If you didn't film a clean plate you can use a solid node and select the backing screen color of the footage. You can get closer to a better matte to be pulled.

There will be times that you have to adjust the solid node color to help with the pulling of the key but the results are much better than just using a single chromakey node or two chromakey nodes for multiples keying. The 4th image uses the solid node for adjusting cleanplate keying assistance.