When the shutter-release button is pressed half-way down, focus and exposure are locked. Where you point the camera before locking focus and exposure can make the world of difference in how well a photo is exposed.
The first photo in this article is poorly exposed. The cameras exposure meter was fooled by the bright sky and underexposed the house, making important areas appear too dark.
The second photo is exposed more correctly. The photographer consciously locked focus on a mid-toned area of the house, indicated by the red dot, then recomposed before fully pressing the shutter button.
A mid-toned area was selected to obtain an acceptable exposure balance that would capture detail and color for the home but not entirely wash out the sky.
In difficult lighting conditions, obtaining proper exposure often involves compromise. The goal is to find the best exposure for the most important areas of a scene.
When using this technique, watch for changes in exposure on the LCD as you preview the scene. Don’t press the shutter button halfway down until exposure looks just about right.