In-Camera Light Meters Aren’t Perfect
The light meter built into cameras these days are much better than even a few years ago in that they can usually get the exposure right (or pretty close to it) in a wide variety of lighting situations. But even the best can be fooled if you have an unusually bright background with a dark subject. Think of a sunny day at the beach or on a ski hill. Even the best of light meters can struggle with this scenario.
How do you handle this situation so that your subject is properly exposed? One solution is to take a few shots with different amounts of exposure bias but that’s just guessing. The best way is to know right off what the exposure should be and, if the in-camera meter suggests something different, you can over-ride right away without trial and error.
The “Sunny f16 Rule” states that the ideal setting in bright sunlight, with a front-lit subject, is an aperture of f/16 and a shutter speed that is the inverse of the ISO setting. As an example, if you have set the ISO to 100, the setting to use would be f/16 and 1/125s, f/8 and 1/250, etc. For cloudy bright, use f/11; cloudy – f/8, etc. What’s that you say: you have ISO set to “Auto”? Don’t. Pick a setting and leave it unless you need to change it. There you go; two tips for the price of one.
Remembering this rule will help you to cope if your camera’s built-in light meter fails to interpret the scene in the way that you want.