Exposure Tips:

Today's cameras are incredibly good at getting proper exposures in auto exposure mode. Unfortunately, they are not perfect and photographers still need to learn the fundamentals of exposure. The following are some helpful tips regarding exposure.

Photographers basically use two types of metering: The first is reflective metering which measures the light reflected by the subject (this is what your camera's meter is doing). The second type is incident metering which measures the light hitting the subject.

Reflective meters:

The in camera light meter is designed to set the exposure so that the subject appears middle tone (18% gray). Most photographers quickly learn that their camera's reflective meter can be fooled if the subject is lighter or darker than middle tone.

If the subject is lighter than middle tone, the camera meter tells you to close down the aperture. You correct for this by opening up the aperture to let in more light. Conversely, if the subject is darker than middle tone, the camera meter tells you to open up the aperture. You correct this by closing down the aperture to let in less light. The amount of adjustment you have to make depends on how far your subject is from middle tone.

For example: If you use the camera to meter a bright white subject like an egret, the meter will try to expose the egret as a middle tone gray. You would end up with a gray bird instead of the bright white bird you actually photographed. If you opened up 1-1/2 to 2 stops from the camera's meter reading, the bird would be properly exposed and would appear white in the photo.

If you use the camera to meter a black bear, the meter will try to expose the bear as a middle tone gray and you would end up with a gray bear. If you close down 1 to1-1/ 2 stops from the camera's meter reading, the bear would be properly exposed and would appear black in the photo.

Incident Meters and the Sunny 16 Rule:

An incident meter measures the light falling on the subject (as compared to the light reflecting off the subject). The sunny 16 rule is a basic exposure rule for bright sunny days. It is also an exposure rule based on the light that is falling on the subject. Under the sunny 16 rule, your exposure for a front lit subject on a bright sunny day would be 1/film speed at f16. For example: If you are using a 100 ISO film, your exposure would be 1/125th at f16.

Since many photographers don't carry incident meters into the field, they often don't learn the adjustments that may be necessary for incident meter readings. This is important because the same adjustments apply to the sunny 16 rule (remember, sunny 16 is a rule based on the light falling on the subject). Generally, you do not need to adjust exposure when you have an incident meter reading or when you have used the sunny 16 rule. However, if the subject is very bright (and near white), or if the subject is near black, you will generally need some adjustment.

The adjustment for non-middle tone (near white, or near black) subjects when using the sunny 16 rule, or an incident meter, are the opposite of those that you would use for a reflective meter reading of the same subject. If you are using the sunny 16 rule (or if you have taken an incident meter reading) and the subject is much lighter than middle tone, you must close down the aperture to let less light in (if you were taking a reflective light meter reading of a white subject, you would adjust by opening up the aperture). Conversely, if you are using sunny 16 on a subject that is much darker than middle tone, you must adjust by opening the aperture to let more light in.

You can test this on a sunny day by photographing bright white, and near black, subjects using both the sunny 16 rule and the adjustments noted above. The amount of adjustment that you will need depends on how far the subject is from middle tone. For example: The normal sunny 16 exposure using a 100 speed film would be 1/125th at f16. However, in order to properly expose for a white egret in bright sunlight, you will need to stop down about 1 stop and shoot at 1/250th at f16. If you don't do this, the white bird will appear over exposed and bleached out.

Nature photographers often have to make snap decisions regarding exposure, so it can be a real advantage to know how to quickly adjust from the sunny 16 exposure for your subject.

The photograph of the raven above was taken based on an adjustment to an incident meter reading.