Here is what EasyHDR does it takes a set of exposures and combines all the information in each to produce a low dynamic range image with the information from the high dynamic range image.
You can see the sky came from the under exposed image and the shadow detail from the overexposed image.
This works very well for astro images see here large image 2.2MB
http://members.optusnet.com.au/~trlee8/lagtrifhdr6.jpg
Bert
Normal exposure---------Under two stops---------Over two stops-----------LDR from EasyHDR