Chroma key the background of an HDR clip in Final Cut Pro

Create a new library and project, and import the green-screen clip and the background clip into the new project. Then, adjust the HUE vs. LUMA curve that's part of the Hue/Saturation Curves effect and apply the Keyer effect. You can save the entire effect as a preset to use with other chroma key clips in this or any other Final Cut Pro project.

1. Create a new Final Cut Pro library.
2. In the Libraries sidebar, select the new library, then set the Library color processing setting to Wide Gamut HDR:
   • Choose File > Library Properties (or press Control-Command-J).
   • Click the Inspector button on the right side of the toolbar.
   • Click Modify at the top of the Library Properties inspector, then choose Wide Gamut HDR.
3. Import the HDR green-screen clip and the background clip into the new library.
4. Create a new project and set the color space to match your original material. For content captured with an iPhone 12, choose Wide Gamut HDR - Rec. 2020 HLG. For content captured with other cameras, use Wide Gamut HDR - Rec. 2020 PQ.
5. Add the background clip into the primary storyline.    
6. Add your green-screen clip above the background clip by connecting the green-screen clip to the primary storyline.

1. In the Video Inspector, click the Color Inspector button.
2. Click the pop-up menu at the top of the Color Inspector, then choose Hue/Saturation Curves from the Add Correction section of the menu.
3. Under HUE vs. LUMA, click the eyedropper tool and select the color in your image that you want to key out. This creates three control points on the curve.
4. Choose View > Show in Viewer > Video Scopes.
5. Click the Video Scopes settings button , then choose Waveform and Luminance (or Luma if you're working in HLG).
6. Adjust the luminance of your key color:
   • For Rec. 2020 HLG formats, including video captured with iPhone 12, use the middle control point you set in the HUE vs. LUMA section of the Hue/Saturation Curves and reduce the luminance of your color key to a maximum of 50%.
   • If you are working in Rec. 2020 PQ, use the middle control point and reduce the luminance to a maximum of 100 nits.

1. In the Effects browser, drag the Keyer effect to the green-screen clip. 
2. To make fine adjustments to the Keyer effect, open the Video inspector to access controls for the Keyer effect.
3. To save this combination of effects to use on other clips you need to chroma key, click Save Effects Preset, set options, then click Save. Learn more about saving effects presets.