For decades prior to the invention of through the lens (TTL) light metering, photographers used handheld light meters to quantify the illumination falling on a scene so they could set the camera’s exposure accordingly. This was the era of the camera as mystery box, when the only way to determine if an exposure was accurate was to shoot a polaroid, wait two minutes and then check the results.
The invention of the digital camera, however, introduced a much more efficient way of working thanks to the “what you see is what you get” nature of the LCD on the back of the camera. This instant feedback revolutionized how photographers dialed in exposures and ushered in a new era of photography. It also rendered handheld light meters all but obsolete.
All, that is, except for those photographers striving for supreme precision in their lighting. Sure, most portrait, travel and street photographers may find that the camera’s TTL meter is sufficient, but what about when a photographer wants to augment with their own lighting, or ensure maximum latitude in a raw file by absolutely nailing the precise exposure they’re after? Handheld light meters are still plenty useful in situations where precision matters.
For example, I recently used my trusty Sekonic L-358 light meter to check the ratio between highlight and shadow in a portrait session. I knew the look I was going for, and the look my client wanted to see, and as I was setting up my lights prior to the subject’s arrival I could use my light meter to adjust the power and position of the lights until I knew they would be almost perfect, even though I hadn’t shot a single test frame.
So if you find that you want to further refine precise lighting setups, or if you’re tasked with matching lighting from another photo, the best way to do it is with the help of a handheld light meter. Here’s how.
LIGHT METER BASICS
There are two fundamental types of handheld light meters: those that measure the amount of light falling onto a scene, and those that measure the amount of light reflecting off of a scene. The former—the kind that measures light falling onto a scene—is called an incident light meter. These are the most common, evidenced by a little white dome over their sensor. When you see an assistant on a photo shoot or a movie set holding a light meter in front of a model or actor’s face, you’re typically seeing them use an incident light meter. (That little white dome, incidentally, is meant to mimic the general shape of the human face.)
The other kind of light meter is a reflective meter, which as the name suggests measures the amount of light reflecting off the scene or subject. This is the way a TTL camera meter works. The only downfall of a reflective light meter is that it’s going to provide a different exposure suggestion based on the tonal values of the things in the scene. For instance, a black cat in a black hat in a black room will reflect one value, while a white cat in a white hat in a white room —with the exact same lighting—will deliver an entirely different reflected meter reading. Incident meters avoid this because they measure how much light is falling on the scene.
In practice, handheld reflective light meters are referred to as Spot Meters. These were very popular with landscape photographers in the film era and adherents to Ansel Adams’ zone system of black and white exposure. With a handheld spot meter the photographer could hold the meter to their eye and look through it to ensure it’s aiming at a specific object in the scene, then measure the relative brightness of those specific elements—the bark on a tree in sun compared to the foliage in shadow, for instance—in order to determine exactly how they want to expose the scene and process the film to achieve their desired result. Used this way, light meters are incredibly precise and powerful and useful as ever, particularly if what’s most important is the exposure value of a specific portion of the frame.
Most commonly, though, when the average photographer is using a handheld light meter they are using an incident meter to measure the amount of light falling on a scene, so they don’t have to compensate for the white cat or black cat subjects.
With spot meters it’s up to the photographer to factor in the subject’s inherent tonal values to avoid over- or underexposures. But the handheld incident meter doesn’t care, because it’s measuring the light before it bounces off the subject. It’s why using an incident meter (the one with the little white dome) is easier for new photographers to understand.
PUTTING LIGHT METERS TO USE
To use a handheld incident light meter, start by dialing in some portion of the exposure values —like the ISO and aperture you want to use—then read the shutter speed the meter recommends. If your key light isn’t constant, if it’s a flash, you’ll need a meter that can trigger it or read the short-duration strobe of light. Most light meters sold these days can read flash, but be sure to check the fine print before purchasing. (Often these meters will be called Flash Meters, and they can read both flash and continuous light with simple changes to the settings.)
Next, position the meter under the same lighting as the scene you’re photographing—whether that’s an architectural interior or a window-light portrait—and press the button to measure the illumination falling on the subject. For a portrait, position the meter in front of the subject’s face and take a reading. For a room, position the meter in various places throughout the scene with the sensor aimed toward the camera.
If you add a reflector or fill light to your scene, take a new reading after each lighting addition to ensure you’ve got an accurate accounting of all the illumination in the scene. If you’d like to isolate an individual light source—to determine the light falling on the shadow side and the key light illuminated area of the subject, for instance—position your hand or body to block the key or fill light from reaching the meter. Better still, turn off all the lights except the one you’re trying to measure so you’re only metering one element at a time. This way you can better understand the ratios between the different light sources.
For portrait lighting—a popular use of a handheld light meter—hold the meter on the highlight side of the subject’s face and take a reading. If it reads, say, 1/125 at f/8 at ISO 100, you can then compare it to a reading taken on the shadow side of that subject’s face. If the shadow side reads 1/125 at f/4 at ISO 100, that tells you that you’ve got a strong 4:1 ratio (four times the light, or two stops) between shadow and highlight, which is pretty bold but not extreme. If your client has asked for a specific contrast ratio (as mine sometimes do) the light meter is an invaluable way to ensure accuracy. Even if you’re not delivering a ratio specific to a client’s request, even if it’s simply because you’d like to achieve a deliberate lighting look, a handheld light meter is a great way to ensure that what you see is really what you get, and prevent surprises and disappointments once you’ve downloaded your images into the computer for a closer look.
