I think it can’t find any matches between the top picture at the bottom two. The ripples in the water would be different, the sky is blown out, and just that little bit of land on the horizon is common, which isn’t enough to get a good match.
With a darker exposure the clouds in the sky would provide more match points.
I use AutoPanoGiga (pay for software) to do my panoramas. It has the benefit of allowing guided match-point determination where you could high-light the horizon land in the two adjacent photos and it’d find matches, then.
I tried photomerging with your images and got the same result as you. Like ssprengel said, there wasn't much in common in the photos. This link may be a helpful reference to you when using photomerge later on:
So I got photomerge to work by simply burning the clouds a bit on the center and right images to give it a little more to work with. In this case its ok because this is the light exposure of an HDR image, so I have the sky covered in the darker exposures.
Here's the workaround with burned-in clouds:
Here's final HDR results (still see the stitch line going thru the middle, will have to work on that):
Thanks for the help ya'll.
The sky and the water look nice, except the brightness discontinuity you’ve acknowledged; however, the grass and the boatman aren’t vertical. Maybe a different projection would do a better job?
Are you starting with JPGs or raw files? Are you blending the HDR by hand or through an automated process? Did you shoot 3 exposures in each position for a total of 9 images for your HDR panorama?
Instead of selectively burning the sky in PS, I would probably have opened all three files in Camera Raw and used the same Highlights Reduction setting to bring down the sky a bit evenly across the entire sky, avoiding the discontinuity you have to work around.
Here are a couple of other things to try:
1. Use file>Scripts>Load Files into Stack and leave the align button at the bottom unchecked.
Expand the canvas size, manually align the photos as best you can and then select all the layers and use Edit>Auto Blend Layers.
2. Try the optional interactive layout (Photomerge UI) for cs5:
How to use: