In one of my first and favorite lessons in B & W photography it was explained that if we wanted our whites to turn out really white and our blacks to turn out really black, we should overexpose and underexpose respectively—around 1/2 to 1 full stop.
The built-in reflective light meter in most SLR cameras is designed to give a correct reading based on a middle gray (think [wikipop]gray card[/wikipop]). For example when metering something like a white wedding dress, the meter takes a reading of the white in the dress and tells you the correct exposure for a neutral middle gray. In this case, since we don’t want the dress to turn out gray we would overexpose to get a crisp white.
This was my answer to a recent annoyance of mine. Often when I would view my photos on a monitor—straight out of camera (SOOC), many would appear slightly underexposed. I realized what I learned above in film could apply in digital too. As I put these principles into practice my pictures turned out punchier and exposed more in the way I had envisioned them (See the above photo of Mr. Happy Feet for an example).
In this case I compensated for what my camera told me was a “correct” exposure.
– ‘Cause cameras are pretty darn smart but lots of time they need our help.
I recently read this article “Exposing or Shooting to the Right” which explains this concept very well.