Sunday, December 30, 2007

Technique (Exposure) - Your Camera's Light Meter

The first camera I owned in the early 1980's had only a spot meter. This type of camera meter measures the light entering the lense from basically one point. Typically, the place it takes the reading is wherever the center of the viewfinder was pointed. Usually the photographer pointed the indicator at his main subject, take an exposure reading, and set the aperature and shutter speed to give this exposure. This is to try to make the main subject properly exposed. However, as noted above, the meter could be fooled into giving an improper exposure when the subject was darker or lighter than 18% gray or if the background was such and there was a lot of it in the frame.

Later, I purchased a Nikon FA. This was the first camera to introduce a multiple area metering system. Basically, multiple area meters check the amount of light coming from a number of areas in the frame. The camera contains a computer which interprets these readings and calculates an exposure. The Nikon FA has a feature the photographer can change to set the camera to either meter a spot or multiple area.

Multiple area metering (it has many names) has evolved. Modern cameras can have settings which allow not only spot metering but all sorts of multiple area metering. The difference in the types of multiple area metering is the areas being metered - concentrating near the center to scattered throughout the area being framed by the camera.

These multiple area metering systems are basically designed to compensate for the different colors of objects in the frame. They are relatively good at giving the proper exposure readings for most situations. Where they typically fail is when a very light or dark area is in a significant portion of the frame, such as bright sunlight coming from behind a subject.

Thus, you can set your camera to meter multiple areas and usually get a good exposure. In conjunction with a camera set to programmable mode, a person with very little knowledge of photography can take good pictures in many situations. However, there are times when the meter will be fooled. Also, there are factors which will affect how sharp the picture will be.

Use a gray card or a substitute to get proper exposures in difficult situations. This is the subject of the next post.

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