How to Use a Light Meter Outdoors

Some digital cameras have a light meter and exposure built in. However, the light meter can get confused in certain cases, such as shooting a snow-covered landscape, when the light meter assumes that all things in the picture are equally reflective.

Using the "Sunny 16" rule helps you understand how to use a light meter outdoors and draw up a table based on exposure values. The rule is based on the fact that the sun is equally bright between 10 a.m. and 5 p.m., so if you know the exposure for sunlight at midday, you can estimate it for cloudy or overcast days. Proper exposure is an aperture setting of f16 for ISO 100.

Instructions

1. Make an exposure chart. If you have ISO 1600, the f16 at 1/1600 is the correct exposure. You can construct the rest of the exposure table by using equivalencies:

   F16 is 1/1600
   F11 is 1/3200
   F8 is 1/6500
   F5.6 is 1/13000

2. When making the exposure chart, keep a few things in mind. Since there are no consumer cameras with shutter speeds as high as 13000, you will need to dial back the ISO in bright sunlight; but if it is a cloudy day, light is described by shadows seen or not seen.

3. Know your shutter speeds. Know whether or not your camera has automatic exposure and light meter settings. Some are automatic and others use a manual light meter.

4. Know the lighting conditions. "Soft Shadows," which is characterized by soft edges, is weak sunlight, and needs one stop more light--or F11 instead of F16 in our example. Cloudy but bright days may require two more stops of light, or F8 and 1/ISO. "Overcast" means no shadows at all, and requires three more stops of light, or F5.6, which is the same as in the shade on a sunny day.

5. Purchase or set your light meter. If you do not have a separate light meter, you may not need to purchase one, if your camera has an automatic light meter setting. In the event it is not equipped, you will need to find the light meter that will give you the results you want for your specific conditions and equipment.

Tips & Warnings

• Pictures of the moon are frequently a problem when it comes to using a light meter outdoors. Since the moon is a sunlit object, set your exposure as you would for a car sitting on the street in sunshine--for ISO 100, F16 would be at 1/100th. If you have a bright, snowy or reflective background, but faces that are not sunlit, you may need to alter the exposure and light meter to an in-between setting for the best pictures. Experimenting with the table and conditions may be necessary until you fully understand the relevant principles.

• Frequently, the automatic mode of the light meter will not pick up proper exposure, so it is sometimes best to use manual modes. Not understanding how a light meter and exposure settings work can cause you to ruin a lot of special pictures.

References

• Digital Grin

Resources

• Stock Photo Guide