Using An Incident Light Meter

This write-up is not designed to cover every aspect of exposure metering; rather, it is meant to explain the use of the Incident Light Meter in a simple, easy-to-understand manner.

- Rohinton Mehta

To understand how incident light meters work, we need to first understand how reflected light meters work. The incident light meter may be going out of fashion, but it is still very important accessory which is not given its due credit in modern times.

A light meter (also known as ‘exposure meter’ or just, a ‘meter’) is a device that suggests proper exposure settings for a given lighting situation. Every modern camera has a built-in exposure meter. You point the camera to the subject and then half-press the ‘release’ button. Before you can use the meter, you first have to set the ISO (the sensitivity of the imaging sensor). You then have the choice of selecting the aperture or the shutter speed. If you select the aperture (Aperture Priority Mode), the meter will indicate the corresponding shutter speed; if you first select the shutter speed (Shutter Priority Mode), the meter will indicate the recommended aperture. If you wish to use the Manual Exposure Mode, you can select the aperture of your choice and then ‘null’ the meter (bring the index mark to the zero position. See image 1). You could also, if you so desire, first select the shutter speed of your choice and then ‘null’ the meter. If you prefer not to get into technicalities, just set the camera to the Program Mode. When using the built-in exposure meter, the meter reads the light reflected off the subject. Hence all camera meters are ‘reflected light meters’.

Exposure basics