I have just read an excellent article on the PixelatedImage Blog about metering with digital cameras. In the ‘good ole days’ (i.e. with film) we used to meter the scene, adjust the camera and expose the film. What this article advocates (and I agree) is that with digital we should be exposing and then metering. As the last line of the blog states from an Asian saying, “Same, same, but different!”
The point being made (very well in my opinion) is that the digital sensor in your camera can hold more information in the higher (i.e. brighter) values than it can in the lower (i.e. darker). This leads to the expression amongst digital photographers than when you take a picture you should “expose to the right”, referring to the look of the histogram you get on the back of your camera. But the advice comes with a health warning. You must shoot in RAW and not JPEG otherwise you lose all the flexibility you thought you had.
Read the article, it does a great job in explaining this.