Quote:
I probably need to get some kind of metering device
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Joan,
Every modern camera has a "metering device" built in. This is how it determines proper exposure for any given light situation. Exposure being the combination of two factors a) how wide the aperture is opened (aka f stop, this can range from 2.8 to 22 and many points in between) and b) how long the aperture is left open (aka shutter speed, ranging from full seconds to many thousandths of a second). Or in other words, how much light, and for how long. These two things combine to determine the amount of light which hits either the film, or in the case of digital, the chip. In very low light situations the aperture would want to open wide for a long time.
It makes this determination based on what it sees through the viewfinder, not necessarily what is in front of the camera.
Some cameras allow the viewfinder to be further separated into smaller "zones" such as, the middle 1/3, or in the case of spot metering, the center 5+-% of the viewfinder. When one of these zones is selected, only the lighting conditions within this zone is used to determine the exposure of the scene. There may be other calculus going on depending on the sophistication of the camera.
So if you can, through any of these methods described in this or the above post, explain to your camera that you would like to expose only for the area of the face, then you will get a proper exposure for that section of the viewfinder. Understanding that other areas of the picture may be either over or under exposed, but for your purposes, you don't really care.
In the following example the girl was standing in front of pure sunlight. If the camera were allowed to consider the entire frame it would have tried to balance all that light coming in and the result would have been a completely washed out face. Instead, I asked the camera to only consider the light on her face for exposure. This gave a pleasing facial exposure and completely over exposed the background, which was fine with me.