Calibrate Your Light Meter

If you are not using your light meter correctly, your images are likely to develop too dark or too light. To calibrate your light meter, follow these simple instructions designed to make the most of this helpful photography accessory. Even though cameras and light meters are both precision instruments, it is possible for them not to cooperate with each other. Fortunately, this problem is easy to discover and even easier to fix.

Assess your target

The first thing you need is a white or neutral gray target. Choose a collapsible target that has one gray side and one white side. Some targets have printed lines on both sides, making it even easier for the camera's auto focus to lock. For the purposes of calibrating a light meter, use the gray side of the target to judge the meter's accuracy with a camera's histogram.

Check the exposure

Mount the target to a light stand, and aim a strobe at it. Have the strobe set up at least 7 feet away, and use an umbrella or softbox to spread the light out even more. Now check the exposure with the light meter by moving the target forward or back until the exposure is an accurate third of a stop. Check the sides, top and bottom of the target to make sure the exposure is evenly spread across the surface. It must not have more than 1/10 stop in any direction.

Spike the meter

Fill the camera's frame with the target, and take a picture with the speed on the meter set to the same value as on the camera. If both the camera and meter are calibrated, the histogram shows a spike in the middle - exactly where you want it. If the spike falls to the left or the right, make an adjustment to the meter in tenths of a stop. Keep adjusting it until the reading shows a spike that is in the middle of the graph. Adjust the target away or toward the light each time you make an adjustment on the meter. Do not change the aperture of the camera but rather the target position.

Once you calibrate your light meter, it can measure light that is perfectly tuned for your camera equipment. Repeat this exercise for each camera that you use in your work. Make note of how you adjusted each camera to remind yourself how to reset the meter, resulting in a great picture every time.