There are few more pieces to this DR/EDR/HDR/XDR puzzle that haven't been discussed much!

One that is basic is that not all scenes are going to benefit from or even really have a very wide dynamic range. Just because a scene and the resulting photo go from light to dark doesn't mean that there is much illumination range at all. Snow, fog, or predominantly one color (this is the tonal range issue!) subject photos probably have a very narrow range and will only be degraded by trying to improve them!

Night scenes are going to lack a lot of range as a rule.

Scenes with a light source in the photo, such as the sun or a very bright light shining at the camera will be the highest DR with very few exceptions if any other object or objects are in the composition.

Another component to this is, can you provide a significant portion of 32 bits of data image to the HDR engine? Adobe Photoshop and Photomatix both work in a 32 bit wide space to combine the images. Then they compress, if needed, to the appropriate output. If you provide a 'standard' range to an HDR engine it may try to 'create' data or spread out the date over an unrealistic range and then those nasty color shifts and chromatic interferences happen.

What are you really going to do with that ultra wide data field image? The multi thousand dollar EIZO monitors that are just about the cream of the crop today, won't display all the data! The best printing technology available in one pass can't print but a tiny portion of that image! Yes, you can improve your potential output but how often is it just going to look, well strange.

When should you shoot an HDR series of bracketed photos? There's a simple rule of thumb:

If no matter what exposure you set the histogram on the camera clips on one end or the other...You might want to consider setting up the tripod and bracketing 4-6 images.

Just be sure you go from all black clip to all white clip or as nearly as is reasonable. In other words the histogram is bunched way to the left of the display for the first image to be included in the HDR composite, to the histogram being bunched up on the right! If your camera displays clipping on the image itself, look for most of the image to display the blue(often the color for black clip) overlay for the first low range data Image. The last or high end of the Dynamic Range should go to red(often the color for the white clip) for most of the Image.

A final note:

The Expose to the Right rule is coming under fire as the assumption was originally that all histogram displays show the same thing. They don't! Chances are that your reasonably new camera has two or more representations (color, intensity, average exposure, etc.) of the image data displayable with the histogram chart. Some of these should not be set to the right! Ever!

Another problem is that some manufacturers bias the display so that a properly exposed photo will show up in the middle of the screen, i.e. they 'curve fit the data'. Predominance of a particular color or intensity in a scene can alter how the data is represented in less sophisticated modes. Just when we thought we had it figured out they got better tools and everything changed.

Finally not all compositions should be exposed to the right as they are dark or have a lot of edge detail (think Ansel Adams El Capitan photographs or every photo you will ever see of the Eiffel Tower) and setting your exposure that way will kill contrast and detail in crucial areas that cannot be recovered.

HDR isn't for every photograph.

I am going to include a link to One HDR photo that I have posted. It is rendered as a black and white. Look at the histogram in the software tool of your choice. It display all those little overlapping peaks where the separate pieces were included in the very wide data set. The color version which I posted somewhere in a forum post and I can't find is riotous, not what you want, but for the B/W final version it worked better. Just one image as an example of expanding (and then compressing again) light and dark!

A HDR Sample:

http://gallery.photographyreview.com...=drg&mcats=all