John McWilliams writes:
Bracketing in RAW gives incredible latitude. Even a single RAW image
can be developed in, say, two different ways, one for the house, and
one for the sky. Then you can layer the two, mask one, and paint on
the mask to reveal the bottom layer.

I've attempted this from time to time (in Gimp). Where the objects
crossing the horizon are buildings it's worked relatively well, but
where they are trees, it's proved incredibly difficult - I've found
they are too fiddly to get right without strange halos around them.

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http://www.greenend.org.uk/rjk/