What you want to avoid
Here is a list of things to be on the lookout for when you process your images. Avoid those and no one should bother you about whether your image is HDR or not.
Halos
A signature of any method to decrease contrast in bracketed images, those appear whenever a dark and a bright zone are very close to each other, and especially on the edges of mountains on the skyline. They most frequently show in the bright areas but can also hide in shadows. You will need to get those right in the tone mapping process, often by reducing micro-contrast. If nothing else will do, then careful cloning can save the day, but it can be difficult and time consuming, and should be kept as a last resort solution.
Ghosts
Whenever some element in your composition moves between frames, there is a good chance that it will show as a ghost figure, since the tone mapping algorithm will mix a little bit of each image to reach its final result. Software has gotten a bit better at handling those, but it is still one of the worst things that can happen. If the ghost is simple enough, it is sometimes possible to use one of the bracketed images on another layer and clone/mask the ghost out, but be prepared for spending a lot of time looking at your image at 300%. Vegetation is hopeless, and I won't even bother bracketing anymore if there are both leaves and wind at the same time. HDR is mainly a technique for static subjects.
Inverted contrast
What HDR really does is reduce the brightness of highlights and increase the one of shadows. But if you take the process too far, you can obtain a situation where two neighbouring zones have inverted which one should be brighter than the other. This usually looks very, very ugly (if you haven't seen it before, open any image in photoshop and apply a strong inverted S curve on luminosity, then try not to throw up). More generally, it is a good idea to try and keep track on what parts of the image should be brighter than others, and verify that your tone mapped image still respects it, as a sanity check. If the sky is darker than the mountains, something is probably very wrong.
Noise
By its very nature, HDR processing will significantly increase noise, especially in the shadows. One way to limit it is to ask the tone mapping software to output an image slightly overexposed, but be prepared for the need of using noise reduction plugins.
Excessive saturation
The scenes we do HDR for are usually very contrasty, so they should also be very saturated, right? Well, not necessarily, no. Also, for some reason, the saturation applied by the tone mapping software seems much more artificial than the one you can get via photoshop. One rule of thumb is to fix saturation as the last step in the processing, just before final sharpening.
Excessive contrast
This is a hard one, and it can be difficult to draw the line and decide what is too much. As said before, though, contrast should not be gained in the tone mapping stage but later, once back on a LDR image inside photoshop. You will have to trust your eye and your memory of the scene. Does it really correspond to your memory of what you saw (and what you felt)? If you were seeing the image for the first time, would your first reaction be "wow, this is beautiful" or "wow, someone had fun with photoshop"?
For this tips i wanna say thanx a lot to my friend Mark David (Amsterdam) for sharing this much of info for all of us...^^
