Proper Main Light Meter Placement


The correct position of the light meter determines the correctness of exposure. Indeed, there’s a reason why incident light meters utilize a plastic dome to see the light before it hits the meter’s sensor, and that reason is undeniably easy to understand; the shape of the dome mimics the shape of the face, and that shape reads the strength of light and shadow relative to a face and gives you a correct and proper f-stop for your camera. It makes no difference what color of skin you’re working with because a correctly metered light will be a perfectly exposed light, and any skin color will be properly represented.

So, what is the correct position of the meter’s dome? In the vast majority of circumstances, the place to hold the meter is directly under the subject’s chin and aimed at the camera. This guarantees the meter reads the three zones of light—the specular highlight, diffused highlight , and transition zone—with an equal balance. The result, if your meter is calibrated, is an exposure that’s so perfect you can go straight to proofs without tweaking Levels at all. When you’re using a calibrated light meter, the amount of time you’ll save is enormous. You will be confident enough with your metering techniques to avoid shooting RAWfiles entirely, if you wish.

Let’s back up for just a minute. RAW files are the digital equivalent of a film negative, allowing you up to 2 stops in exposure compensation. RAW files are a digital gift because in tough shooting situations they can really save your bacon. Each RAWfile is worthless by itself, however. It must be “processed” via digital software before it can be used as a JPEG, TIFF, or any other format.

As you know or can imagine, the amount of time required to process a large batch of RAW files can be enormous. Imagine a wedding photographer who shoots two or three thousand shots in RAWformat over the course of the big day. Each shot may take 3 to 4 minutes to tweak, plus the time necessary to process the files into a TIFF or JPEG format (depends on the speed of your computer). Think about the amount of time you might save if you nail the exposure, especially in JPEG format, straight out of the gate.

If you feel you must shoot RAW, set your camera to shoot large JPEG files and RAW files at the same time. When you download, separate the RAWs and JPEGs into separate folders. Look at the JPEGs first. If you find JPEGs that need to be tweaked, use the RAW files to do so. If the JPEGs are fine, trash the RAW files or just burn them to a disc. Your time savings will be huge.

Metering for correct exposure in the studio is quite easy. I’ve photographed a few test images just to show you how foolproof it can be.

Let’s begin with the light set at zero degrees to the lens axis (i.e., directly over the lens). I used a simple parabolic reflector as a modifier for this test. It’s rather contrasty, but it will demonstrate the principle nicely.

In image 2.1, you’ll see there is a full range of tones, from the bright whites of the subject’s teeth through the shadows of her hair.

The correct position of the light meter, in at least 90 percent of all situations, is directly under the chin and aimed directly at the lens. This will guarantee the meter will read all three zones and deliver an average reading that will give you a proper representation of those zones. See image 2.2.

At 22.5 degrees from center, the angle of incidence begins to change. You may have been taught in photo class that the “angle of incidence equals the angle of deflection,” and this is absolutely true. The meter angle stays the same, straight on to camera, but you begin to see some changes in the specularity of the light because it’s now aimed at different planes on the face and reflecting directly into the camera from some of them. See image 2.3.

At 45 degrees, the shadows deepen because there is no fill on the shadow side. The exposure, measured with the meter still aimed at the camera, still produced a perfect exposure when the strobe generator was adjusted to the target exposure, f/10 for this example. See image 2.4.

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At 60 degrees, which is more than most attractive portraits will tolerate, a meter reading aimed at the camera still yields a beautiful result. Shadows and highlights are properly represented, even though the image is very contrasty. See image 2.5.

So, what happens if we aim the meter at the light? At 60 degrees, what can the difference be, after all? Interestingly, the difference can be quite major.When you aim the meter at the light, you will only measure the brightest part of the light, not the average of highlights and shadows we’ve been measuring so far. With the meter aimed at the light, note the difference in shadow density and highlight brilliance between the previous examples. The inference is clear: most circumstances do not require the meter to be aimed at the light. Aiming it at the camera will produce more consistent results almost all of the time. The first image was made at the previous aperture, the second was made with the reading given by aiming the meter at the light, not at the camera, a 1/4-stop difference. See images 2.6 and 2.7.

The easiest way to add fill light to your image is to bring in a white bookend or any other kind of white fill to add light to the shadow side. I’ve never been a fan of adding another strobe as fill. I much prefer a fill card of some kind because it will not add any shadows of its own. Be advised that, even at 3 feet away from the subject, the extra light that bounces in will affect the overall exposure. In this case, introducing the bookend added 1/3 stop of light to the overall exposure, which meant I had to either take the exposure down at the source (as I would recommend) or move the main light straight back a few inches. Either approach will maintain the ratio of any other lights that may have been set. This image, metered with the dome aimed at the camera, is a perfect example of how bounce fill can open up the shadows without looking like a second source of light. See image 2.8.

Metering a profile is different in that it’s one of the few times you’ll need to aim the meter at the light rather than the camera. This assumes that the light is coming from in front of the profile (and from the side,

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relative to the camera). When the light is coming from any direction less than the 60 degrees we previously discussed you can meter, with confidence, with the dome facing the camera.

When the light is coming from 90 degrees to the side, if we were to meter with the dome aimed at the camera, the amount of shadow would throw off the accuracy of the reading, causing a poor exposure. See images 2.9 and 2.10.

Once you’re satisfied with the reading and f-stop, set and meter any other lights you wish to use. I reintroduced the white bookend and added a hair light, powered to the same f-stop as the main light. A small piece of black foamcore, mounted on an accessory arm, created a flag that blocked off part of the light striking the background. The result (image 2.11) is a visually interesting and lovely image. This is a perfect technique for many portrait applications, from beauty and glamour to graduation portraiture.