First you need a photo to convert. I decided to use this one:
This is straight out of the camera, no changes to the photo
Step 1 Convert
the image to black and white but tweak it with the sky as your
priority. Don't bother with the ground at this point. The only thing
you're after is contrast in the clouds.
Something like this: Nice contrasty clouds
Step 2 Now
open a copy of the image and place it in a layer above the previous
one. Convert it once again but with the ground as your priority. The
sky will probably bleed out a bit when you do this.
Like this: Contrast in the ground
Step 3 Add
a layer mask from black to white to your last conversion. Let the shift
cover the horizon, this will hide the clouds but show your properly
exposed ground.
The mask should look like this: Layer mask that covers the horizon
The end result will look like this:
If
the horizon is more complicated the mask will need more work, but it's
worth the effort. If you want to you can add an adjustment layer and
change the hue of the entire photo depending on what feel you're after.
