Exposure II (Light Meters)

Exposure II (Light Meters)

by William Lulow

A light meter is a device for measuring the amount of light on a given subject. It is important to understand the various types of light meters in order to understand how the metering system in today’s digital cameras work.

The REFLECTIVE light meter measures the amount of light that is reflected from the subject. It is usually pointed at the subject from the position of the camera. (In this case, it is contained in the camera itself and measures light as it is reflected from the subject through the camera’s lens). It works fairly well for most conditions, but can be “tricked” by shiny objects within the scene and other factors that affect exposures.

The INCIDENT light meter measures the amount of light that falls on the subject through a translucent sphere. The reading is taken from the subject’s position. This is a very dependable method of determining a correct exposure for the subject as a whole. It can even be used for specific points within a scene if used properly.

The SPOT meter is a device which also measures reflective light, but does so for only about a one-degree coverage.  It is excellent for measuring light reflected from a subject at moderate and long distances. I have used this meter extensively to measure light on a performer during a concert that I used to cover with traditional film cameras. Now, you can use your digital SLR’s meter settings to achieve pretty much the same results. 

Most good digital cameras these days, have incorporated the attributes of reflected readings. They can measure an overall scene as well as various types of SPOT readings from “center-weighted” readings to actual spot readings. Use your camera’s manual to understand what settings to use for the type of photographs you intend to make.

Most of my concert photographs were made with the use of a SPOT meter so that I could accurately measure the amount of light reflected from the musician’s face. In addition, these days, I’m using the spot feature of my camera’s meter to measure the exact place I want to expose for in the shot. I can then decide where I want the most detail to show in my image. Once I’ve done that, I can then decide how much detail in both highlights and shadows I want to show. This is a conscious decision on my part as the photographer. I’m not letting the camera decide the exposure. I’m only using it to obtain readings off the places in the image I decide!

So, I’m actually slowing down my approach to exposure determination by THINKING ABOUT what I want to show and what will be important in the image.