Tips for Tricky Exposure Situations Page 2
2 Bracket Exposure
What you just did in item 1 is a bracketed series of exposures. It's a good idea to shoot such a series any time you're in doubt about the correct exposure: Shoot one frame at the exposure you think is right, then shoot additional frames, giving more and less exposure than that. With slide film, bracket in 1¼2-stop increments; with print film, full-stop increments should do. You'll use more film, but you'll assure that you get a properly exposed image.
3 Understand Your Meter
There are two basic types of exposure meter: incident-light, and reflected-light. Incident meters measure the light incident (falling) upon the scene; reflected meters (which are the type built into cameras) measure the light reflected from the scene.
Using an incident meter is simple: Hold it right in front of your subject, point its translucent hemisphere at the camera lens, and expose accordingly. The problems are (1) subjects that are in different light than where you are, and too far away to get to; and subjects that are light sources, such as fires.
Reflected-light meters are calibrated to reproduce the metered subject as an "average" medium tone. This is fine when your subject is indeed a medium-toned one. If the subject is brighter than a medium tone, the meter will see more light and thus call for less exposure (the meter doesn't know what you're pointing it at or how you want it reproduced in your photo; all it knows is how much light is striking its sensor). The result will be an underexposed (too-dark) bright subject and scene. Conversely, if the metered subject is darker than a medium tone, the meter will receive less light and thus call for more exposure; the result will be an overexposed (too-light) subject and scene.
The key to using a reflected-light meter is to remember this simple rule: Whatever you take the meter reading from will be reproduced as a medium tone in the resulting photograph. So, the simplest way to get good exposures with a reflected-light meter is to read medium-toned subjects. If you meter a bright subject, give more exposure than the meter suggests. If you meter a dark subject, give less exposure than the meter suggests. Ansel Adams' Zone System is the most effective way to use a reflected-light meter (for black-and-white photography, anyway--it involves adjusting developing times to control contrast, and changing developing times with color films alters color balance as well as contrast), but just keeping the above rule in mind will suffice in most situations.