I wrote this post in early 2009, so I am sure that many of my readers haven’t seen it. I decided to repost it because it is an important concept for digital photographers to understand.
As you may have heard, with digital, unlike film, your goal should be to expose your image as brightly as possible, without blowing out important highlights. In other words, your histogram should be as far to the right as possible without going over the edge. This method is now called ETTR — Expose To The Right.
What is the histogram? It is a graph of the tones in your images, from pure black (blocked up, no detail) at the left edge, to pure white (blown out, no detail) at the right edge.
I recommend that you set your camera to show the histogram next to the image on the LCD screen, so that you can see right away how succesful you are with your exposure.
In this case, the exposure is ok: