If you use studio strobes for lighting, and your images are consistently too light or too dark, it’s probably not your fault. It’s entirely possible that your light meter and your camera are not on the same page. I know that sounds improbable; after all, they are both precision instruments. But, while all manufacturers produce equipment to close tolerances, it’s possible for a meter and camera to both “pass” their respective Quality Control tests but not be in agreement with each other. Fortunately, it’s really easy to discover if the two machines are out of sync, and it’s really easy to fix the problem.

You will need a neutral gray or white target. You can find collapsible targets from BalanceSmarter.com and Lastolite.com, both of which are gray on one side, white on the other. The difference between the two is that the BalanceSmarter product has printed lines on both sides, to make it easier for your camera’s auto focus to lock on to it. These products are invaluable for Custom White Balance as well and are available in several sizes.

For this exercise we’ll use a gray surface, which will allow us to use the camera’s histogram to judge the accuracy of the meter.

Begin by mounting the gray target on a light stand, and aiming a strobe at it. You will get a more even light by setting the strobe at least seven feet away from the target and using a softbox or umbrella to spread the light even more. Check the exposure with the light meter and move the target slightly forward or back, if necessary, until the exposure is a perfect whole f-stop, like f8 or f11, or a perfect third of a stop (f+.03 or f+.07). Check the top and bottom and both sides of the target as well, to make sure the exposure is even across the surface, no more than 1/10 stop off in either direction.

Fill the frame with the target (you can turn off auto focus if you can’t get close enough with your lens) and take a picture. I try to just shoot the center portion. Be sure your shadow does not fall on the target. Also, be sure to set the ISO on the meter to the same value as the camera. If your meter and camera are speaking the same language, your camera’s histogram will show a spike right in the middle, which is exactly where you want it.

All good flash meters allow you to make adjustments, in tenths of a stop, in how they read the light. If the spike in your first image is left or right of center, you’ll need to make an adjustment to the meter, basically tricking the meter into reading the light stronger or weaker than it did before. All meters will make adjustments differently, depending on the manufacturer. Consult the meter’s instruction manual to determine how to do it for your equipment.

Regardless of how it’s done, all you need to do is adjust the meter until the reading it gives you produces a histogram spike that’s in the middle of the graph. You’ll need to adjust the target toward or away from the light each time you make an adjustment, so that the reading the adjusted meter gives you is the same as the reading you started with. In other words, don’t make any changes to the aperture of the camera, just adjust the target position.

Once calibrated, your meter will measure light that’s perfectly tuned for your camera. If you use more than one camera, repeat this exercise for your other gear. It’s possible that your other camera(s) will require a different adjustment or none at all. If that’s the case, a marked piece of white tape or a white label on the bottom of the camera will remind you how to reset the meter. My Sekonic, for example, offers two different calibration methods, one of which is invisible. The other shows the adjustment on the meter’s screen every time it’s turned on. This is the one to use if you have more than one camera in play because you’ll immediately know if the adjustment is correct for the machine in your hand.