Picking up from where we left off in a previous post — where we discussed the correct use of histograms in reading the exposed scene and not the actual exposure — we shared that a hand-held light meter will give you an accurate exposure reading every time, regardless of the conditions.
This month, we share with you the different types of light meters, how to use them, and what type of light meter is best for your shooting. For starters, let’s take a look at the three types of metering systems that are in light meters. You can buy dedicated light meters for each type of metering system, or a meter that does all three types of metering.
In reflected mode metering, the meter is reading the intensity of the light that is reflected off a the subject and onto the metering sensor. This is the basic principle of how your in-camera meter operates, by reading the light coming through the lens off of your subject.
The colors and tones of objects reflect light differently. For example, white snow reflects an intensity of light that is vastly different than black sand. Because of this, the light meter has to assume that the subjects in the scene are classified as “middle gray” on the grayscale, meaning that 18% of the light striking the subject is reflected back. The resulting meter reading provides an exposure that would render the object reflecting the light as middle gray.
If you were to take a meter reading off of white snow, the meter would be fooled into thinking that the snow is reflecting back only 18% of the light, which would be inaccurate: white snow is not middle gray. The resulting exposure would be underexposed, as the meter would be giving a reading that would make the snow middle gray.
Similarly, if you were to take a meter reading off of black sand, the resulting picture would be overexposed as the meter would provide an exposure setting that renders the black sand as middle gray.
If you were to place an 18% gray card — a card that accurately represents middle gray and reflects 18% of the light back — into a scene and take a meter reading off of the card itself, the resulting meter reading would be an accurate and correct exposure for that scene.
Why? Because the light meter is accurately reading the light reflecting off of the card. It is important to remember that the intensity of the light falling on the subject is a constant. Only the intensity of the light reflecting back off the subject will change, depending on the color of the subject (remember white snow vs. black sand).
So if the meter is looking (read: assuming) for 18% middle gray in its exposure, give it 18% middle gray to meter off of and you will get a correct exposure.
1) While your in-camera meter is based off of a reflected mode metering system, it is “intelligent” in that in can read colors in the scene through it’s matrix/evaluative metering system to provide a very close “guess” to the correct exposure. Remember that it is always a guess, regardless of how close it gets to the correct exposure. If you place an 18% gray card in the scene and switch to spot meter mode, reading just the gray card, the exposure will no longer be a guess but accurate.
2) The higher-end hand-held light meters also include a spot meter function, similar to the spot meter function in your camera. The difference is that the spot meter function in the hand held meter is a separate optical lens system that has variable zoom control, from a 3-degree to 1-degree spot. Essentially, a very narrow reading area.
The meter provides the exposure setting in the optical spot meter finder, but remember that this reading is still a reflective metering exposure, assuming the object is middle gray. However, this method of metering is the de facto standard of all professional landscape photographers, as it provides the ideal evaluative exposure control by isolating the exposure value of individualized areas of the composed scene.
As we said above, the intensity of light falling on a subject doesn’t change. Rather the amount of light reflected off the subject is what is the variable in different exposure readings. This is the basis for the “Sunny 16” or “Basic Daylight Exposure” (BDE) rule that we use in all of our workshops. Since the sunlight is a constant that doesn’t change, we can calculate with certainty what the correct exposure would be for any given scene.
But if a cloud passes in front of the sun, or it is overcast or stormy, the light is no longer a constant as it is being filtered by the atmospheric conditions that are blocking the light. When that happens with the Sunny 16 rule, we are back to estimating what the correct exposure would be under those conditions.
That is where an incident meter comes in handy. Quite handy.
An incident meter measures the light falling on the meter’s white plastic dome and then provides an exact and correct exposure for the intensity of light it registers. Because it is reading the light falling on the subject to calculate exposure, the subjects color or reflectivity is irrelevant. The resulting exposure will render the scene — regardless if it is sunny, overcast or stormy — in the correct exposure.
Cameras do not have incident meters, as they are only reading the reflected light. Incident metering can only be found in hand held meters. And the reliable accuracy of incident meters makes them a mainstay for most professional photographers.
1) There are two variations of incident meters on the market, based on the size of the incident meter’s white plastic dome that registers the intensity of the light. The common belief is the larger dome registers a more accurate exposure reading due to the larger surface area capturing more of the light falling on the dome. Naturally, the light meters with the larger domes cost more.
2) One of the negatives about incident meters is that it can only read the light falling on the meter itself, not the light falling on a scene not where you are standing. For example, if you are photographing a river scene that is in shadow but where you are standing on the bank is in the sun, you would have to move the meter to the location you are photographing in order to get an accurate meter reading. In nearly all of these situations, photographers revert to the reflective meter, using the optical spot meter to ‘zoom’ in on the are in the composition and then calculate the correct exposure from the 18% gray meter reading.
3) There is a common back-and-forth discussion amongst photographers on the topic of where to point the dome of the incident meter: toward the camera and lens, or toward the light source. When using an example of photography a person that is side lit by the sun, such as with a setting sun, the argument goes that: a) it should be pointed at the camera lens so that the dome on the meter and the subject’s face are oriented the same, so that the light falling on the dome is the same amount that is falling on the face; or, b) it should be pointed at the light source because you are exposing for the illuminated portion of the face, and the dome needs to be fully illuminated in order to accurately render the correct exposure. So which is correct? Well, both of them are correct. The first argument will provide an exposure that is ‘averaged’ between the illuminated and shadow areas. The second argument will provide accurate exposure of the illuminated portion of the face, disregarding the shadow area.
The third option of metering is exclusive to reading light from flashes or studio strobes.
Hand held light meters can either trigger the flash through a sync cord or radio trigger (such as built-in PocketWizard transmitter) providing an instant reading on the meter. The other option is to put the light meter in cordless mode where you push the button on the meter and it waits for the flash to fire to measure the light.
Because shutter speed is irrelevant in flash exposure (as long as the shutter speed is at or below the camera’s published sync speed), the light meter provides an aperture reading based on the ISO setting.
The common flash meter reads the intensity of light that falls on the white dome. (Technically, this form of metering is also incident metering but the light meter unit is “watching” for the short burst of light that comes from the flash unit, ignoring the ambient light.)
As with incident and reflective meters, you can purchase a flash meter-only model that can only read the light from a flash unit. While this model is considerably cheaper than a model that can do all three types of metering, the higher-end meters can do all three forms of metering: reflective, incident and flash. Using a flash-only meter can also limit you in your ability to balance flash with ambient (see notes below).
Also, a combined reflective/incident/flash meter allows you to read the intensity of the light from the strobes utilizing either reflective or incident metering modes. In incident mode, the light falling on the white dome provides an accurate exposure for the scene. In reflective mode (used through the built-in optical spot meter), the meter would provide an exposure based on the reflected 18% middle gray. This is utilized when determining and controlling the exposure of a background, such as a white or colored backdrop/sweep, by metering an exact spot of the backdrop.
1) The higher-end meters that have incident flash metering mode also have a white dome that retracts into the unit. This allows for metering of multiple flash units that are at different intensity at different location in the studio or location.
If you are using one strobe as the primary flash, or key light, and another strobe as a fill light, by retracting the dome and pointing it at the light source, the meter will read only the light falling on the retracted dome head, not contaminated by the light coming from the fill light strobe. Then metering only the strobe that is the fill light, you can determine the correct exposure that is not as powerful as the key light but also provides fill light.
2) Many flash meters will record multiple “pops” of the flash to evaluate the accumulated bursts of strobe resulting in a final exposure setting.
3) A meter that is exclusive to reading only light from a flash or strobe, while cheaper, does limit your ability to read the ambient exposure through incident metering and balancing the exposure with the flash reading. Since the shutter speed does not affect the exposure from a flash or strobe (as long as the shutter speed is at or below the camera’s published sync speed), a higher-end light meter will provide a balanced exposure between the ambient light and the light from the strobe.
What is the best light meter?
While there is no single light meter that is better than others, it is important to look at the feature sets of each type of meter and determine what works best for you.
You can purchase a low-cost incident meter that does only incident readings, which will work just fine for nearly all ambient conditions, but you would be limited if you need the other metering modes (reflective metering, spot metering, and flash metering) or the higher-end features including wireless options, radio triggers, touchscreen, camera profiles, or cinematography controls.
So where to start?
Entry-Level Light Meters
An excellent starter light meter to get familiar with hand-held metering is the entry-level analog (seen at left) or digital meter (seen at right). These meters are small, compact, lightweight and easy to operate.
The analog meter is battery-free, but requires turning a dial to align the needle for the correct reading. The digital version, albeit more expensive, provides the exposure settings via the meter’s LCD screen. The digital version also has the ability to switch to reflective mode and flash mode.
Advanced Control Light Meters
A small step up in price and a big step up in features brings you to the meters featuring touch-screen interface and capabilities. These allow for far more expandable controls of the lighting situation, including automatic filter compensation.
In addition, the Sekonic Litemaster Pro L-478DR model features PocketWizard wireless technology enabling touchscreen control of remote flashes connected to PocketWizard ControlTL receivers.
Touch the on-screen sliders to adjust power levels of Nikon or Canon Speedlights mounted on PocketWizard FlexTT5 transceivers or select studio flash units connected to ControlTL receivers. The L-478DR also incorporates PocketWizard Standard Channel and Quad Zone capability and can trigger any flash with a PocketWizard connected to it, including those with PocketWizard modules built-in.
Professional Light Meters
The higher-end hand held meters available today handle incident, reflective and flash metering, but also include the critical and important optical reflective spot meter, down to a 1-degree measuring sample. These meters are a considerable step up in price but are also rich with features, including average exposure, evaluative exposure between flash and ambient, saved exposure settings, dual ISO settings (for quickly switching between two different ISO settings), wireless radio trigger, and evaluative dynamic range HDR metering.
A key element in the professional meter, such as the Sekonic L-758DR meter, is the ability to calibrate the light meter to create a camera profile through integrated software applications and test targets. This ensures that the readings from the lightmeter match the camera’s true ISO, optical variations, dynamic range and sensitivity, in addition to post-production workflows. This additional precision ensures that the shooting environment is dialed-in exactly to the necessary final image output.
The Sekonic L-758DR meter also includes the ability for wireless radio triggering of PocketWizard connected or enabled flash units. And it is built with an all-weather, dust-proof and splash-proof housing.
The Sekonic L-758DR meter costs approximately $635 from B&H Photo.
So which meter is the best to purchase? Plan on your handheld light meter lasting for several decades of use. While future light meters will certainly add improved features and options, the core of the light meter will not change: the ability to accurately read light.
While your photography demands today might be simple analog incident readings, you need to ask yourself “Will that light meter serve my needs next year, or five years from now, or 10 years from now?”
We recommend purchasing a light meter that provides a feature set for where you want to take your photography skill set. The hand held light meter is a tool in your tool bag, and it will only improve your abilities within the bounds of what it can provide for you.