Exposure: using a light meter

Now that we've talked about balancing shutter speed and aperature, totday's tutorial will help you figure out how to decide the exposure needs. A light meter is usually located inside the viewfinder of an SLR, but handheld meters can also be purchased. What you must remember is that a light meter can only measure the amount of light in the subject area, the determination of shutter speed/f-stop and the depth of field and action effects that those have, must be made by the photographer.


The actual method of integrated light meter will vary from manufacturer to manufacturer. There will be a light or needle displaying the needed amount of light for the scene and another indicator showing the amount of light allowed in with the current settings. By moving the aperature and shutter speed dials, you will see an instantaneous result of the exposure needs and can balance the "current" indicator with the "needed" indicator. For instance, you have an f-stop of 8 and a ss of 125, but the internal meter shows the number 500. You can either stop down the f-stop one position or increase the shutter speed one position. Either choice will reduce the light to the correct exposure, but you must choose whether you want the fast shutter speed to stop the action or the small f-stop for the greater depth of field.

A light meter works well in the average scenario, but there are instances when it can be easily fooled by the conditions. If the subject is much brighter or much darker than the immediate surroundings, then the meter will be thrown off. You have probably experienced this by taking a picture of someone standing directly in front of a window. The meter adjusted for the brightness of the window, and the person was underexposed. Since the light meter is clueless as to what you actually want to adjust for, there are several ways to deal with the problem.

1. Make a close-up reading of the subject. This way the meter is filled with the subject and will expose for it. be careful to ensure, though, that when you are doing this that you are metering on the object in the same light that it will be in when you step back to shoot. Also make certain that your shadow or the camera's shadow don't fall onto the area that you are metering.


2. Use the palm of your hand or a gray card if you are unable to get close to the subject (wildlife, a concert...) Again ensuring that you are using the same angle of light for your hand as for the subject, place your palm in front of the lens, then open 1 stop larger than the meter indicates. This is because the skin tone of the average palm is approximately twice as bright as the average subject. Instead, you can purchase a gray card from a photography store. So named because it is gray--18% reflected light which is what the average subject is. These are extremely useful but can be hard to tote around in a camera bag. The palm is great because it is always present.


3. If all else seems to fail, bracket. In instances where your hand cannot be in the same angle of light, and you cannot get close to the subject, first take the picture at the setting that the light meter recommends. Then take the picture 1 and 2 f-stops above and below the suggested settings.

Now that we've covered the basics, it's time to play! You definitely want to experiement a little bit before an important event. An instructor once told me to experiment with an orange as their dimpled texture will react very differently with different exposure settings. Have fun!