Cameras see differently than we do. While we have the ability to see everything in color, the camera’s meter sees and measures only how light or dark a scene is. It sees only tonality: black, white and a bunch of shades of gray in between. The shade in the middle of the gray scale is what is called middle gray. Middle gray is achieved when it reflects only 18% of the light that falls on it.
Grey Scale
The largest goal in photography is to capture your images with accurate exposure or in better terms: for the camera to record your scene or subject as you see it. How can this be achieved if your camera or handheld meter only measures in tonality and brightness? In the same lighting scenario, every shade or color reflects a different amount of light and this is where a light meter can come in handy.
Do You Really Need a Light Meter?
Most of us have been taught to get it right in-camera and to only rely on post-processing for any fine-tuning, but now that there are tools such as Lightroom to correct image characteristics after the fact such as exposure, do you really need a light meter? The simple answer is this: it can only benefit you by providing you with more accurate results.
My Sekonic Flash Master L-358 with its younger sister, the Sekonic LiteMaster Pro L-478DR.
Pros
- Accurate meter readings
- Can measure the power of your light source as well as the light reflected off of a subject for a versatile reading
- Compact tool
- Easy to use
Cons
- Can be expensive depending on the features you need and the model you choose
In a photo editing program, altering your exposure is really guessing at what looks like the correct exposure, but unless you are super lucky at guessing that exact number, it won’t give you the exact exposure of the image as you originally saw it. While your in-camera meter can give you a good meter reading in some situations, it does not cover, with accuracy, all scenarios including some tricky lighting situations such as backlighting or a scene that is almost all dark or all light. So in a nutshell, a light meter can make all the difference in exposure accuracy.
Types of Meters Readings
There are two main types of meter readings: Incident and Reflected. Handheld light meters have both reflected and incident reading capabilities.
Incident
Incident metering is sampled from the subject or scene’s position and it is a reading of the amount of light falling on the subject or scene. It does not measure the amount of light reflecting off of a subject therefore its readings are usually consistent and more accurate than reflected meter readings. Incident metering gives the most accurate exposure reading for a most situations and subjects because it is not influenced by differences in reflective properties from a subject or scene. It is only influenced by the light source falling on the subject or scene. When using incident metering, set the ISO and shutter speed on the meter and the meter will measure the intensity of your light source and suggest which aperture to set your camera at with those ISO and shutter settings for proper exposure for that light’s intensity level.
Here I used a handheld light meter to read from the model’s location from overhead
and from where I stood below to shoot her picture to get the correct exposure.
Reaching your desired result requires you to know and understand your manual settings and the relationship between settings to achieve the that desired result. For instance, if you know you want your subject and all of the background to be completely sharp and in focus, you wouldn’t want a fast aperture because fast apertures tend to be soft and create a shallow depth of field. If you want to focus only on one part of your subject or scene with the rest of the image being slightly blurred out, you wouldn’t want a slow aperture because slow apertures tend to capture much sharper scenes. So knowing the relationship between settings to achieve your intended result when using incident metering is crucial.
Reflected
Reflected metering is sampled from the camera’s position and is a reading of the intensity of light “reflecting” off of the subject or whole scene. This type of metering is something you can do in-camera or by handheld light meter. In camera, the reflected meter is the digital scale tool with digital pins that appear or disappear on the right or the left of the center of the scale by adjusting the aperture and shutter speed. In-camera, a correctly exposed image is when the scale is zeroed out to the center, but this does not always mean it is the correct exposure.
Below are images of what your in-camera meter readings would look like for over, under and proper exposure using reflected metering. The in-camera meter is the vertical bar on the right side of the LCD monitor with the plus, zero and minus signs.
The first image shows that my image is too bright since the pins are illuminated more toward the plus sign. According to the in-camera meter, to get the correct exposure in average lighting conditions, I would have to adjust my ISO, aperture and/or shutter speed to drop my exposure to get the pins to zero out to the center of that scale.
The result of shooting at this reading would be overexposed.
The next image below shows that my image is underexposed because the pins are illuminated more toward the minus sign. According to the in-camera meter, to get the correct exposure here, I would have to adjust my ISO, aperture and/or shutter to increase my exposure to get the pins to zero out to the center of that scale.
If I captured the image at these settings, the result would be an underexposed image.
In the next image, you will see that the in-camera reflected meter is zeroed out and the image now appears to be correctly exposed.
Correct exposure for this controlled lighting scenario.
To get a good exposure reading in-camera, the goal is to adjust the shutter and aperture so that the center needle is the only needle remaining. Using your in-camera reflected meter really only works on average subjects in average lighting conditions. Sometimes the meter will incorrectly assume the exposure based on variances in subjects and scene. They can vary based on several differences such as color, tonality, contrast or background. Think: a bright white wedding dress or a groom’s black tuxedo. These are two different extremes and can create an incorrect meter reading when the light meter is trying to obtain a middle gray.
Subjects or scenes lighter than middle gray appear lighter and because the goal is to get to middle gray, the meter will recommend or automatically adjust your camera settings to underexpose your image to get that bright subject to a middle gray. But what if your scene is bright white and your subject has darker skin or if your subject is backlit? If you tone down the exposure, your scene may be correctly exposed, but your subject would be a silhouette.
Here is an image where I correctly exposed only my subject using my in-camera meter.
If your subject or scene is darker than middle gray, the meter will recommend or automatically adjust your camera settings to overexpose your image to reach the middle gray. But what happens when you have something black in the scene, perhaps a groom in a tux, and you want to keep his suit black? If you bring up the exposure, his suit suddenly becomes gray instead of black.
In both cases, exposure compensation may be needed, and that is a whole other topic in and of itself. Just keep in mind, when you are shooting a subject with a scene in the background, you want to expose for your subject, not the scene.
Features to Look for in a Handheld Light Meter
A good handheld light meter will have the three metering capabilities: incident, reflected and flash modes. If you shoot video, a color temperature meter like the Sekonic C-700 SpectroMaster Spectrometer would be an ideal tool for you. If you are looking for the percentages of where your exposure is coming from (ambient, LED, fluorescent and/or tungsten continuous lighting vs. flash or strobe lighting), Sekonic meters are known to possess this feature. My current light meter, the Sekonic L-358 Flash Master, along with the Sekonic Litemaster Pro L-478DR has this feature. Those folks that work in studios may find the need for a meter to be able to fire their strobe – “wirelessly” being a bonus. Some Sekonics such as the Sekonic L-758DR Digital Master have this feature. Some meters feature the ability to read light from a 1-degree angle. This can help you take control of the exposure from any distance to the subject, which is helpful when you cannot get close to the subject.
How to Use a Light Meter
It’s really important that before you learn to use a light meter, that you know how aperture, shutter speed and ISO all relate to and work with each other. For instance, when you are working in a studio and you want a shallow depth of field because you want to blur out the insignificant background to highlight your subject… you know you want your ISO to be as low as possible to eliminate unnecessary noise and you want to set your shutter speed to your highest sync speed. How do you obtain a correct exposure at a faster aperture? Your light meter will tell you the aperture you are currently at based on the ISO and shutter speed settings you enter. From here, you will know if you need to move your light source forward or back or change the intensity of the light source by powering it up or down to reach the aperture number you want.
Place the light meter under the subject’s chin.
When using incident metering with flash or strobes in studio, you would do the following:
- Set the ISO on your camera based on your lighting scenario, typically as low as possible in studio which is usually 100 or 200 based on your camera model.
- Then you would set your shutter speed on your camera based on your camera’s highest sync speed.
- Next, you would mimic those two settings on your light meter.
- Turn your lights on and attach your flash or strobe trigger to your camera.
- Rotate the knob at the top of the meter so that the white ball is fully exposed.
- Place the light meter under your subject’s chin and press the button on the side of the light meter.
- Trigger your strobes either by pocket wizard or by taking a picture.
- Read the aperture number the light meter is suggesting for correct exposure. This is the number you will set your aperture to in your camera for correct exposure.
Alternatively, you can scroll the combinations of apertures and shutter speeds from that reading to get a combination for your desired result.
Alternatives
18% Grey Card
The Lastolite Ezybalance Collapsible Grey & White Exposure Aid Card provides two purposes: the white side assists in helping you obtain the perfect white balance while the 18% gray side aids in gaining proper exposure.
To gain your proper exposure settings using a gray card:
- Set your aperture and ISO to your desired settings for the shot.
- Set your camera to spot metering mode and select only the center focus point.
- Aim your lens at the gray card center focusing on the center crossing lines and hold your shutter button halfway down.
- Then, using the guide in your viewfinder, adjust your shutter speed until you have zeroed out your reflected meter scale.
- Take the picture and your resulting image should have correct exposure.
Expoimaging ExpoDisc 2.0
While the Expoimaging ExpoDisc 2.0 is another alternative for white balance, it too is another tool that aids in gaining proper exposure using your camera as the meter. Since many photographers have many lenses and the ExpoDisc is literally used for less than 60 seconds to get your settings, there’s no need to have an ExpoDisc for each lens size that you have. Simply purchase a larger ExpoDisc and manually hold it over the lens for results.
To gain your proper exposure settings using an ExpoDisc:
- Stand at the same position where your subject will be located.
- Hold the ExpoDisc over your lens so that no ambient light seeps through the sides.
- Using your in-camera meter, adjust your ISO, aperture, and shutter speed settings until you’ve reached your desired result and have zeroed out the in-camera meter.
- Take a shot and your resulting image should be correctly exposed.
Conclusion
Your in-camera meter can be a convenient tool, but using your in-camera meter alone may not always yield you accurate exposure results. When combined with an 18% gray card or an ExpoDisc, it can get you better results, but your best bet, really, is to invest in a good handheld light meter. It is a convenient, portable and versatile tool that will always measure to give you accurate exposure readings, both incident and reflected. A handheld light meter will not be a tool that sits around in your camera bag collecting dust, if your goal is to always have accurate exposure for your images.
Dawn M. Wayand is owner and photographer for Dawn M. Wayand Photography. She also owns and runs NYC Digital Photography Workshops, a successful 5-instructor, 3,500 member photography group in NYC. Since inception in 2011, NYCDPW has been geared toward helping photographers of all levels find their own unique style and hone their craft through various group and private workshops.
