Pulling a Clean Green Screen Chroma Key In DaVinci Resolve
DaVinci Resolve may be known as one of the world’s best color grading platforms, but its compositing/chroma key tools are just as impressive.
Top image: background from Dume Studios
In some cases when working as a colorist, you may be given pre-keyed footage. Your editor or VFX artist may have already gone ahead and keyed out a green screen shot for you, and will simply send you a composited shot to color grade.
In other instances though, you’ll need to pull the key yourself. If you’re like many colorists who are DaVinci Resolve experts, but don’t necessarily have a lot of experience with other VFX software (such as Nuke or After Effects), you’ll likely be tempted to pull your color keys right inside of DaVinci Resolve. The good news is that Resolve has an extremely powerful keyer built right in, and you can absolutely use it for your chroma key work. This short tutorial from FilmmakerCentral will show you just how to do it:
Here’s a breakdown of the steps in the video:
1. Set up Your Timeline
Before getting started with your chroma key work, you need to set up your timeline by placing the background plate on track one and the green screen shot on track two, just as you would in any other NLE.
2. Use the Qualifier
Once you move back into your “color” tab on DaVinci Resolve, you’ll want to use the eyedropper/qualifier tool to isolate the green background. You can use the highlight visualizer to show you a black and white image of what’s selected vs. what isn’t.
3. Invert Your Selection
By default, your selection will of course be on the green elements in the frame. For the purpose of this process, you need to invert your selection in the qualifier tab. The goal is to have your background appear completely black, and the subject fully white.
4. Fine Tune
With your selection still highlighted and inverted, adjust the threshold of your settings in the qualifier tab until you get the cleanest result possible.
Image from Shutterstock
5. Adjust the Blur
Once your key is looking solid, use the “blur radius” setting to add a little bit of softening to the edges. This will help to hide or smooth over any imperfections in the process.
6. Create Alpha Output
With your key now complete, you’ll need to tell DaVinci Resolve how to composite your footage. The first step is to right click in your node tree and select “Add alpha output.” You then need to drag a line from your green screen node (using the small triangle at the bottom of the node) to your alpha output, which will sit just under your normal output on the right side of the node window.
7. Fine Tune Some More
Now that you can actually see your image composited, you may notice some green spill or other areas of the key that still need to be fine tuned. Go back into your qualifier tab and fine tune the settings some more until you achieve an end result you’re satisfied with. One of the features in this video that was highlighted is the “in/out Ratio,” which can help to clean up your edges.
Got any DaVinci Resolve tips/tricks/techniques to share? Let us know in the comments below!