Russ of the four original shots you posted up top, the first two are very well-done and entirely believable. I might have guessed that the first one was HDR if you hadn't told me, not because it doesn't look natural but just because I know getting such nice shadow tones and local contrast would be difficult in a single exposure. The second shot, I wouldn't even have guessed it.
The last two have that "HDR" look that I don't like. It comes from too much local contrast and an unrealistic tonal distribution. This is espcially true in #3 where there's just way to much local contrast giving it that crunchy, digital, over-processed look. It's also not very realistic that the shadow areas of the foreground are so bright relative to the sky.
The last shot has the same problem, as well as what I call photomatix-sky syndrome, which is uneven color/tone in the sky along with halos where the sky meets the treeline. The relection is also too bright.
If you're using Photomatix Pro with, here are my tips for natural-looking results:
- Don't crank the 'Stength' slider to 100, usually something in the 50-75 range will be plenty.
- Go easy on the luminosity and micro-contrast sliders
- Do crank up the Light Smoothing slider, maybe not to 100% but generally speaking the higher you go with this slider, the more realistic the results will be.
- Black/White sliders should usually be somewhere in the 0.1-.02 range.
- The shadow/highlight smoothing sliders are also useful for local 'hotspots' that have gotten ugly.