Whether you've got a DSLR or you've turned your point-and-shoot into a super camera, those fancy features are useless if you don't understand them. Want to capture a perfectly exposed picture? Learning to use your histogram is a good starting point.
Photo by Dilip Muralidaran.
If you've ever taken a picture and thought it looked fine on your camera's not-so-perfect LCD screen but find the exposure's completely off when you get it on your computer, that's where your camera's histogram comes in. How-to blog Make Use Of has a good primer and explanation of exactly what a histogram does. In short: "The Histogram is basically a graph showing the brightness distribution of an image with pure black on one end, pure white on the other and grey in the middle."
Overexposed photos result in a loss of detail in the picture, and are often represented by when the graph is bunched up on the right side. (You can see an example on the left.) Conversely, underexposed photos, meaning the photo details are obscured in the dark, are represented when the histogram graph bunches up on the left side.
A more balanced histogram will depict the pixel representations spread across the graph. On both extremes, the graph will taper off, like below.
Keep in mind that it's often difficult to achieve a completely balanced histogram for most photos. Contrast in the different tones of the foreground and background typically makes it difficult. The background or the sky will be overexposed in most scenic pictures, for example. The graph doesn't have to be perfect, but if the graph is scrunched up against either side, it's a good idea to review your images to see if it looks OK.
Got your own tips for getting a balanced photo? We'd love to hear them in the comments.