Nature confronts us with scenes of high contrast, for example the sun shining through a tree. Human eyes can deal with this much better than artificial cameras: when looking through the tree, we may still see that the sky is blue and contains clouds, and that the leaves are green, while a camera might only see black silhouettes against a blindingly white sky. That’s because the human eye has a higher “dynamic range” than a typical camera. One way to address this problem, in a limited way, is a very good (and expensive) camera. But there is another, cheap way for smartphones: get an app that takes several shots of the same scene with different exposure times, and computes a final, improved image using the combined information from all those shots. A tried this with my Android smartphone, a Samsung Galaxy Nexus, using the app “HDR Camera+”. First, I took the following shot without HDR, a forest track when the sunlight came from the front and was reflected off the ground. In the darkest patches of the image, we can hardly see the leaves, and in the brighest patches the reflection is so strong that we cannot see any structure:
Next, I took a shot of the same scene with HDR Camera+. Note how well we can see the leaves in the darkest patches now, and that we can also see more structure in the brightest patches. The HDR image is very close to what my eyes actually saw. (They saw a bit more detail still.) So HDR clearly brought an increase in realism.
Strangely enough, one might still consider the first, more unrealistic shot to be the better one, because the exaggerated contrast has an artistic, film-noir feel to it. But that was involuntary, so it can hardly count as a reason to stay away from HDR.
Of course, even from a technical point of view, the HDR shot is far from perfect: the bright patches in particular look slightly artificial. I needed a dozen or so experiments, each consisting of shooting some scene with and without HDR, to get a feel for the strengths and limitations of the method. Considering the low price of the app, I can easily recommend to give it a try.