Sometimes the right exposure isn’t the best exposure, or at least the one you want to use. You may not want to it with every shot, but there are times when you might want to under- or overexpose a photo to get a desired effect.
Used often in fashion photography, there is what’s called the high-key effect, where the picture is overexposed. This can hide flaws in a person’s skin by blasting them out and leaving little or no detail and emphasis other than the darker features, such eyes and lips.
You can go the other way and expose for the highlights. In most scenes there are a range of tones that go from dark to light. If you expose for the lighter parts, the middle and lower values will go dark, leaving detail in the highlights. While not for every picture, it can be used to create the dramatic feeling of moodiness or even foreboding.
This first picture of some of the seats at the Banner Island Ballpark is of what would be considered a “normal’ exposure. If you set your camera on an autoexposure mode, it would look a lot like this. Save for the bright highlights and deep shadows, you can see detail in most areas of the photo.
The second picture of the same scene is shot exposing for the highlights. In this case, they are so bright that some are still a little blasted out, but the shadows have gone into an abyss of blackness, and even the midtones are so dark as to carry very little detail. But it’s that very darkness that gives the picture a ominous aura. The dark repetition of the seats imparts the feeling of Imperial stormtroopers or Sauron’s orc army marching off to battle.
So you can use exposure to not only capture a scene but to create a feeling or mood. Experiment with your settings. Do what is known as bracketing, changing your f/stops and/or shutter speeds incrementally up and down as you shoot. You just have to remember that the “correct” exposure isn’t necessarily the right one.