I was playing around with a high contrast pano and came up with a
modification to the Layer Mask method described here -
Here are the usual steps:
1. Stack the darker image on top of the lighter image.
2. Select the lighter image layer and copy it.
3. Select the darker (top) image layer and click on the layer mask icon.
4. Hold the Alt key, and click on the layer mask.
5. Hit Ctrl V to paste the copy of the lighter image into the layer
6. Apply a Gaussian blur (usually around 40 pixels) to the layer mask.
7. Click on the lighter image layer and you'll see the results.
At this point, you can do some tweaking by applying a level adjustment
layer above the lighter image, but below the darker one as well as
adjusting the opacity of the darker image layer.
Here's where I have modified it with success (at least for this
1a. Select the lighter image and duplicate it.
1b. Repeat this so that you have two duplicate layers.
1c. Set the blending mode on the top duplicate to Multiply.
1d. Uncheck all the other layers except the duplicates, then merge
1e. Take this new duplicate layer and duplicate it again.
1f. Set the blending mode on the new duplicate to Multiply.
1g. Make sure only the two duplicate layers are visible, then merge
1h. You now have a really ugly layer that is very high contrast. :o)
1i. Use this layer for step 2 above (you will be deleting this layer
6. Apply the Gaussian blur, but this time try going to the max of 250
7a. Delete Mr. Ugly layer.
Basically, this seems to make the layer mask more prohibitive, so that
less of the lighter layer gets affected by the layer mask.
You can also simplify steps 1b through 1i (just thought of this as I'm
writing this email) by adding a levels adjustment layer above the copy
of the lighter layer, but below the darker one, then sliding the black
triangle way up to the right until much of the light areas turn very
dark. Merge this adjustment layer with the copy layer and proceed.
Let me know what your results show.