If you use a digital camera, you may have noticed a little box that appears on your LCD screen when you’re composing a picture, with a graph of peaks and valleys that shifts around as you move the camera. This is the Histogram. It shows how well the sensor is able to capture the full range of tones from lightest to darkest and still retain detail in the image.
I’ve never really understood how to use it, but courtesy of Mr. Dario, here’s an excellent and brief tutorial. I can see the usefulness of the histogram in landscape and other still shots where you have some time to think about the image you’re taking and make the necessary adjustments to ensure perfect exposure.