Exposure - the pitfalls
Given the sophistication of today's digicams you would think that it's almost impossible to take a bad exposure. However, there are still situations where even the best metering system will struggle. Realizing when to override the camera's setting is the key to successful images. Typically white overcast skies, snow scenes, or dark subjects against dark backgrounds will fool your light meter
When shooting into the light such as with sunsets or backlit portraits, or landscapes shot into the sun, the brightness of the background will cause the subject to record as a silhouette. This can produce stunning results, but if you want your main subject or the foreground to be correctly exposed, you must increase exposure by 1 – 3 stops depending upon the background's brightness. Another method is to aim your camera down to exclude the sky and meter from the foreground, or in the case of sunsets take a substitute reading from a midtone area of sky and bracket exposures. For a backlit portrait you could also try to use fill-in flash which will make for a nice rimlighting effect.
A dark background with a small brightly lit subject can be problematic too. A typical example would be a theatre scene with a subject lit by spotlights against a dark background. For a correct exposure take a meter reading from a midtone area such as the stage floor not lit by direct spotlight and bracket exposures by 1 stop either way.