Exposing Scenes that are Lighter or Darker than Average
Scenes that are light overall, such as a snow scene, can look too dark in the final photograph if you make just an overall reading or let an automatic camera make one for you. The reason is that the meter will make its usual assumption that it is pointed at a scene consisting of light, medium, and dark tones, and it will expose the film accordingly. But this will underexpose a scene that consists mostly of light tones, resulting in a too-dark final photograph. Try giving one or two stops extra exposure to such scenes.