Q How can I override my cameras automatic metering system

A: As we discussed earlier, most built-in light meters are designed to operate "automatically," which means that when you adjust one of the exposure controls, the meter will internally adjust the other to maintain its recommended Zone V exposure. There are two types of built-in meters.

Aperture-priority meters allow you to choose the aperture you prefer and the meter will adjust the shutter speed.

Shutter-priority meters allow you to choose the shutter speed you prefer, and the meter will adjust the aperture.

To use an exposure other than the one recommended by the meter, you will have to override these automatic functions using one of the following methods, depending on how your camera is designed (check your owner's manual).

Manual Setting. If your camera has a manual mode, you can set both the aperture and shutter speed to the exposure of your choice. For example, if the meter recommends an exposure of f/11 at 1/30 for an area you wish to print as Zone III, you can simply change your setting to either f/22 at 1/30, or f/11 at 1/125. These exposures are equivalent and are both two stops darker than the meter's recommended setting (Zone V).

Exposure Compensation Dial. This function allows you to change the meter's recommended exposure by up to three stops darker (-1, -2, -3), or one to three stops lighter (+1, +2, +3). Some cameras use (x1/2, x1/4) for darker exposures and (x2, x4) for lighter exposures. Refer to Appendix P if the use of these exposure factors is not clear.

Memory Lock. This function allows you to take a meter reading of a given area of the scene, lock that recommended exposure into the meter, step back, and use this exposure for the whole picture. Because the meter's recommended exposure is Zone V, this means finding a part of the subject that you previsualize as middle gray in the final print and locking in the recommended exposure for that area. Some photographers carry a Neutral Gray Card with them to use in situations like this. A variation on this procedure would be to meter an area you previsualize as Zone III and stop down two stops from the meter's recommended exposure.

Film Speed Adjustment. If your camera has no other way of overriding its automatic function, it is usually possible to change the meter's recommended exposure by resetting the ISO/ASA. Remember that when ASA numbers double (for example, from ASA 400 to 800), the amount of exposure requires halves. Halving your ASA setting will increase the exposure by one stop. Review "Measuring Zones," page 31, Chapter 4. For example, imagine that you are metering a wall and your camera recommends f/16 at 1/60 for a film rated ASA 400. That exposure would render the wall Zone V. To place the wall on Zone IV, change the ASA from 400 to 800. The recommended exposure would then be f/22 at 1/60 or equivalent. To place the wall on Zone VI, change the ASA from 400 to 200. The recommended exposure would then be f/11 at 1/60 or equivalent. Remember to reset the ASA to your normal speed for that film after taking the picture.

There are cameras with DX code-reading systems that automatically set the ASA for you, and there are some "fully automatic" cameras that do not allow you to override the metering system. The Zone System can't be effectively used with these cameras.

Digital Cameras For Beginners

Digital Cameras For Beginners

Although we usually tend to think of the digital camera as the best thing since sliced bread, there are both pros and cons with its use. Nothing is available on the market that does not have both a good and a bad side, but the key is to weigh the good against the bad in order to come up with the best of both worlds.

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