Araora Desert: Photo manipulation

Here is a class task where I was given an image of a desert landscape and had to manipulate

so that the sky was replaced and the original landscape fit to the new sky.

I decided to replace the sky not only with one of night posing the challenge of changing the exposures of light to dark but with the added luminosity of the Aurora Borealis.

Here I have copied the blue channel of the initial desert image in order to isolate the contrast between the sky and land, I further push this contrast by adjusting the settings in the curves menu.

I then duplicate the original layer to create a black and white mask in order to create a gradient mask .

here is the top layer and the sky with the gradient mask showing that it fades at the bottom, this allows for the base layer to hold onto the original colour scheme and have the newly added colour scheme of blues and greens on top as light.