Compositing in Davinci Resolve – Sky Replacement

Sometimes you have a nice image, but with a sky that just isn’t right for the story. So how do you replace the sky with another without leaving Resolve? In this tutorial I will show you a simple way to replace the sky in an image.

I have an image of a castle and an image of a sun which I will use to create the beginning of a night scene with a castle and a moon.

On the EDIT page I put the sun on V1 and the castle on V2.

Now I go to the COLOR page and select the castle on V2. Then I use the picker (Qualifier) to create a key for the sky.

So far so good, but how do you use this key for the actual composite?

In the Nodes panel – select “Add Alpha Output” from the drop down menu.

Then drag a line (dotted) from the key output (blue arrow) of node 1 to the Alpha Output.

Now you see the composited image. I found that there was some garbage in the key so I added a Window as a garbage matte.

But the key is the wrong way around!! So I went to the Key panel and selected to invert the key Output by selecting the icon (red circle).

Now the composit started to look the way it should, but I needed to fix the position of the sun, it needed to be further up.

This was simply fixed using the Sizing panel on the Sun image on V1.

I adjusted the Tilt of “Input Sizing” and I was done…..

Or at least I thought so. The key was fine, but the sun image shook a bit, so I needed to Stabilize it. I selected the Sun on V1 and went to the tracker and set it from “Window” to “Stabilizer”, tracked the shot and selected Stabilize, now it looked much better.

Now that I was happy with the composite I could start grading the shot and create a night shot where the sun became a moon.

On the Sun shot I did all the grading in Node 1.

And on the Castle shot I added a Serial Node and did the grade there.

As you can see, the key from Node 1 still goes to the “Alpha Output”.

And here is the result. Pretty simple and works most of the time, it really depends on how good a key you are able to get from your sky.
Good luck!

©2014 Nikolai Waldman