Exploring the wonderful world of double exposing images.
First you take two images. One with appx. +1.0 EV and then one with appx. -1.5 EV.
Put the darker image on the front layer. They should end up looking somewhat like this:
Then you can either mix them together 50% vs. 50% or use a mathematical formula to
blend the two images. I think the formula (the 3rd picture) is the proper choice in most cases.
The formula i came up with to mix the two images is like this. This formula should be run on the front layer (the dark one.):
R = R
G = G
B = B
A = 255 - ((255-(r+r+g+g+g+b+b)/7) * (255-(r+r+g+g+g+b+b)/7)/255)
After this, you might want to apply a gamma of 0.71 to get the gamma back into place.