The 24-105mm lens at 24mm does have a bit of corner vignetting and the HDR processing amplifies that quite a bit. Normally I just use the RAW files from the camera in the HDR software but for this I first corrected for the vignetting in Canon software and saved them as TIFF files for the HDR processing.
This first file is the normally exposed scene prior to any lens correction:
|24mm, f/5.6, 1/180 sec., ISO 100|
Here is the same file after correcting for lens aberrations including distortion:
Here is the five file HDR processed end result using the Painterly 2 presets on Photomatix Pro:
Here's what the image would look like without correcting the RAW files first:
Finally, the geography portion of the post. This cropped section of the image shows Peebles Island, Waterford, Saratoga County in the foreground. The sandy beach is on the tip of Van Schaick Island, Cohoes, Albany County and the shoreline on the left is mainland Troy, Rensselaer County.