An incident meter measures what kind of light

Not quite. An in-camera reflective meter is a great tool. In almost all situations, however, an incident light meter will be more accurate. Many handheld light meters measure both incident and reflective light. As mentioned, there are times when an incident meter is just not feasible, which is why handheld meters often have the ability to measure both incident and reflective light.

To understand when to use one measurement over the other, you need to know how each kind of light meter works, and why. A reflective light meter, such as the one in your camera, measures the intensity of light reflecting off of a subject. The light hits your subject, bounces off of, and then is measured as it hits the reflective light meter. The measurement is taken from the position of your camera. Reflective light meters assume that all subjects are of percent reflectance, or have a mid-tone of neutral gray.

As a result, the measurement can be affected by variations of color or tone in a scene. Wait, what? I know, it all sounds so technical.

Let me try and simplify. An incident light meter measures the light falling on the subject, and will be the same no matter what, unless you change the intensity of the actual light. So, if the subject were holding a mirror, or wearing a highly reflective running jacket, the intensity of the light being measured would be much greater than if the subject was dressed as a cat-burglar wearing all black. If a subject is more reflective, it will obviously reflect more light, making the light hitting the meter more intense.

Most reflective meters have a few different modes to choose from, each measuring the reflected light slightly differently.

Spot Metering: A spot meter measures only the light in a small area of the frame, usually in the very center. You may want to use a spot meter when the subject is the brightest part of your image, such as a swan on a bright day, or a moon in the night sky. Subjects that are darker than gray like a black cat will reflect less light and produce an exposure that renders them lighter—in other words, a gray cat instead of a black one. There are two basic methods for measuring light: You can either take a reflected reading by measuring the light reflecting off of your subject, or you can take an incident reading by measuring the light as it falls on the subject.

Both types of metering can produce precise exposures if you know how to interpret the data that your meter supplies. Many Sekonic meters give you both metering options—along with some sophisticated features not found in even the most advanced cameras with built-in meters. All light meters, regardless of the type, are designed to measure light in a consistent way. In the Zone system of exposure, this middle gray is known as Zone V.

Handheld reflected light meters including built-in camera meters read the intensity of light reflecting off the subject. And because most reflected readings are taken from the camera position, they generally take in a wide area that can include many different reflective surfaces or colors that can bias the meter reading.

A reflected meter will provide different readings for, say, a white cat and a black cat—but it will provide an exposure that records both as the same middle gray. Similarly, a pristine fresh-fallen snow and a black coal field will be recorded as the same color: medium gray.

A reflected meter will also record a red apple and a green apple as the same tone—even though in reality they reflect vastly different amounts of light. Handheld incident meters read the intensity of light falling on the subject and are usually taken from the subject position.

Because they are not affected by variances in subject color or reflectance, incident meters accurately record the amount of light falling on the subject. In the majority of situations, an incident reading is extremely accurate and records tones, colors, and values correctly.

Spot meters also allow you to average readings from several brightness areas within a scene. You can take the meter reading somewhere else, as long as the light is the same as it is at the subject position. Often, when I am doing landscape work, I'll just stand in front of the camera to do the incident reading rather than walk about a long distance into the scene. In cases where you cannot get to the subject, and the light is completely different than where you are located a lighted stage during a concert, for example , you cannot use an incident meter.

A reflected light meter would be necessary for that. In the real world, there are situations where it isn't quite so simple. What if the subject has both bright sunlit areas and deep shadows? Where do you place the meter? What about backlit scenes? We'll begin with the easiest lighting situations.

On the next page, I'll show you how to use the incident light meter in normally-lit scenes. The knowledge that I am sharing took many years of study and practice to attain. If you find it valuable, please donate through my Paypal button below.

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