Cameras and Compromises
While you work with images in a camera, you're constantly making compromises. Where to focus, what to exclude, how to frameall of these questions come into play when trying to decide what to capture in an image. Here's the problem: When you're using your camera to take a picture, the camera can only focus on a specific area of an image, from an exposure point of view. This fact adds another level of compromise to your images.
When you look at a scene, you're viewing it with one of the most sophisticated instruments in the worldthe human eye. Your eyes are capable of seeing detail, definition, and tone with much greater range than any camera offers. If you're standing outside looking at the front of a house, you also may be able to see the sky above the house and the ground below it, and even see inside the house through the windows. That wide range of vision can be measured in stops in a cameraand it almost always surpasses what you can do with a DSLR. The camera focuses on a smaller range of tone, and sometimes when you take a picture the resulting image doesn't really meet the expanse that you were able to see with your eyes.
Photoshop lets you get back some of that image's moment in time, by merging exposures in a variety of ways. HDR photography has recently made this capability available to everyone, especially with HDR Pro built into CS5, but I think sometimes a simpler solution would do just as well. Let's take a look at some possibilities.