This beginner tutorial gives a simple introduction to keying using the Luma Keyer for a sky replacement. The initial intention is to use the keyer to separate the sky background from the foreground based on luminosity.
By experimentation, we find out that the blue channel works even better than the luma channel. This also means that using any other keyer for blue screen should work as well, perhaps even better.
The full training course covers keying in a systematic way, step by step, and also discusses edge treatment, spill / despill, combining different keyers and much more.
This example is only meant to be a simple composite to get you started with keying in Blackmagic Fusion.
This tutorial is taken from the full training course: Blackmagic Fusion: Your Journey from Beginner to Expert