HDR techniques can help photos – even if it is only a single-image RAW file where the HDR technique is applied. I’ve had success with this in HDR Express, HDR Expose, Photomatix Pro, and Dynamic Photo HDR software. However, HDR can be overdone and this is when a photo goes from looking realistic to totally (or partially) unreal. Here is one major flaw I see in most HDR photos, and even in the ones that are well-done.
Just because HDR can bring out every detail in the shadows and highlights, that doesn’t mean that it is best for a photo. My objective in photography is to use all of the dynamic range possible to faithfully represent what I saw when I was taking the photo. My eyes may be able to make out some detail in the shadows, for example, but that does not mean that I value those details in my overall view. Neither should my photo. Those shadows should remain primarily dark. The same goes for the highlights.
A rule I keep in mind when I look at the histogram of a finished photo, I want to have it off of either end – no blocked out shadows, and no blown out highlights, but I don’t want the histogram to be very far from either end. This idea alone keeps the shadows dark with just a hint of detail – similar to what I saw when I was there. And the same goes for the highlights where I may have been able to make out some detail, but they were very bright. A photo needs this light and dark in order to make it visually stunning because contrast of the overall photo is everything – it is the dynamic range of the overall photo to its fullest. If the histogram is brought in too far from either end, then the photo ends up looking “flat,” dull, and lifeless. There are plenty of examples of these out there. All bad.
Another casual rule I use is that I use HDR on single photos and I’m less tempted to over compress the dynamic range. This is mainly because it isn’t there because a single RAW file does not have as much dynamic range potential for HDR as if I shot three bracketed shots at -2, 0, and +2 EV. With a single file I have to be much more conservative with my use of HDR and dynamic-range extending techniques.
So, why use HDR at all? Because HDR stretches that histogram and thereby stretches that dynamic range as well. Your eyes have more dynamic range than your camera can ever capture, so you want to extend the dynamic range of your photos because they will look better to the eye and more like what you saw when you took them. You just don’t want to compress the dynamic range too far with HDR. Use it for what it is good for – extending dynamic range. Don’t use it to see every last detail in the shadows and highlights at the expense of the light and dark areas of the photo!