Metering Techniques:
How to Use an Incident Light Meter for Digital Photography

In my Introduction to Handheld Exposure Meters tutorial, I explained that incident light meters are often the best choice because, unlike reflected light meters, they cannot be fooled by unusually bright or dark subject matter. The incident meter avoids that problem by simply ignoring the subject altogether!

Instead of being pointed at the subject, the incident meter is pointed away from the subject, toward the camera. This allows it to measure how much light is illuminating the scene. The meter's light sensor is covered by a white translucent dome, which simulates a three-dimensional subject. In the real world, objects receive light from all directions. The incident meter's dome is also lighted from all directions, or most of them. It does not see light coming from behind the subject.

 

Some incident light meters from my collection.

The Sekonic L-758DR is a modern multipurpose meter that includes an incident meter and a one degree spotmeter in one unit.

The Gossen Ultra-Pro (Mastersix outside the USA) is basically a reflected light meter, but it has a small incident light dome that slides in place over the meter cell. Because a larger dome is theoretically more accurate than a smaller one at measuring light that comes from the sides, Gossen sold the "Luna-Sphere" attachment shown on the Ultra-Pro in the middle. In practice, the small built-in dome works fine.

The Minolta Flash Meter IV is a system meter whose capabilities could be expanded by a multitude of accessories that added reflected light metering, spot metering, and even the ability to meter through microscopes. The "Flat Diffuser" shown above the meter is one of the most useful accessories. It is used for incident metering when photographing flat objects, like artwork, and for measuring lighting ratios with studio lighting.

The big spherical diffuser at the top is one of the more unusual items from my collection. It is an accessory made by Topcon, a now-defunct Japanese camera manufacturer, back in the 1970s. When fitted to a standard 50mm lens, like a filter, it allowed you to take incident light readings using the camera's built-in through-the-lens exposure meter.

 

How to Use an Incident Meter

At its most basic, an incident meter is incredibly simple to use. You simply stand near your subject and point the meter's white dome directly back toward the camera (or the place you'll be standing when you take the picture if you don't have the camera on a tripod). Make sure the meter is in the same light as the subject, then push the meter's measuring button and set your camera with the settings the meter gives.

What if you cannot get close to the subject? 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.

 

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