Response to Bracketing

There are a few basics you need to know: 1. The F stop is calculated by taking the focal length of the lens (the distance from the lens to the film) and dividing it by the working diameter of the lens. The focal length is printed on the front of your lens. It's stated in millimeters. 2. For a fixed focal length lens (i.e., not a zoom lens), the focal length is a constant. The "standard" lens for most 35mm cameras has a focal length of around 50 millimeters. The working diameter of the lens is changed when you open or close the lens diaphragm (when you open up or stop down the lens). 3. If you have the lens diaphragm set so the working diameter is 12.5 millimeters, then the F stop is 50/12.5 = f4. 4. When you move from one F stop to the next, you are either doubling or halving the exposure. f5.6 is half the exposure of f4 and f2.8 is twice the exposure of f4. So in your example, if the light meter gives you a reading of f5.6 at 1/125 sec, you will get one stop overexposure if you manually set the lens aperture at f4 and you will get one stop underexposure if you manually set the lens aperture at f8. 5. I would recommend an introductory book on photography from your local bookstore; it would be far easier than trying to surf the web for this type of information. Good luck.

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