When taking light meter readings, you must be sure the reflected light that influences your light meter is actually from the object you want to photograph. Stray light, backlighting, large dark areas, and shadows can all cause erroneous light meter readings. When using a light meter, be sure that shadows are not cast from the light meter, camera, or yourself. When a hand-held light meter is used, the distance of the light meter to the subject should not exceed the shortest dimension of the object; for example, when taking a light meter reading

of a person's face that is approximately 9x6 inches, you should hold your light meter about 6 inches from the face of your subject when taking the meter reading. When using a light meter that is built into a camera, be sure to focus on the image before taking a light meter reading.

CAUSES OF FALSE LIGHT METER READINGS

There are a number of reasons why light meters give erroneous or bad readings that produce underexposed images. You can prevent these bad readings by being aware of the conditions that cause them.

Light Entering the Viewfinder

Light entering the viewfinder and falling on the viewing screen can cause underexposure. Most TTL meters read the light falling on the viewing screen from the lens. When strong lighting is coming from behind the camera, it can influence the light meter. When an occasional underexposed frame in an otherwise successful series occurs, the cause may be light entering the SLR viewfinder. Make a point of shielding the view-finder if you do not have a rubber eyecup. When you use a tripod, have the camera set on automatic and cap the viewfinder to prevent exposure errors.

Incorrect Film Speed Setting

When the majority of frames on a length of film are consistently underexposed or overexposed, the most likely cause is you have the wrong ISO set on the film speed dial. For black-and-white film and color reversal film, it may be possible to compensate for this in developing if detected before the film is processed.

Bright Subject

A bright object or highlight area can affect the sensing area of a spot or center-weighted TTL meter. This results in an underexposed image. To prevent this from occurring, you should ensure the sensor is pointed directly at a midtone within the scene, and use this as the camera exposure. When you frame and compose

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Figure 4-20. 4x5 Graphic View II camera.

your image, the light meter may indicate a different setting. Be sure to leave your camera set at the indicated midtone setting. Normally, light meters that take integrated or averaged readings of the field of view cannot be fooled in this instance. But remember, even integrated systems cannot cope with extremely bright areas that take up a significant portion of the frame.

Bright Background, Dark Subject

When you are taking photographs that are back-lighted or against a light background, there is always the danger of underexposing the main subject (unless you use special techniques to fill in shadows, such as using a reflector or a flash unit). Be careful to take a reading from only the shadow side of the subject in these situations.

Too Little Light

The most frequent cause of underexposure is trying to take pictures when there is not enough light. Light meter readings are not very accurate at these low-light levels. When you want to make photographs under these conditions, be sure to use a tripod and bracket to provide more exposure than indicated by the light meter. You also can switch to a higher IS0 film. Some of the high-speed films marketed today can provide remarkable results.

There are several other causes that may cause your images to be exposed incorrectly. Some of the most common causes are listed as follows:

Wrong camera settings are set when transferring information from a hand-held light meter to the 4-26 camera. This can also occur when you attempt to override an automatic camera.

Using a camera with TTL metering and placing a color filter with a high-filter factor over the lens.

Wrong aperture setting when flash is used.

Shutter speed is not synchronized with camera flash.

Aperture or shutter speed setting is knocked while carrying the camera. Always check the camera setting before taking a photograph.

Weak or incorrect battery in the light meter.