How to Use a Light Meter in Photography for Great Results

Don’t you hate it when your photos are too light or too dark? This happens because the light meter, also known as an exposure meter, has not been used well. If you enjoy using any auto exposure mode, you may not even be aware of how to use a light meter in photography.

An accurate light meter will help you or your camera choose the optimal exposure settings. All digital cameras have an in-camera light meter. Handheld light meters are also an option if working with older film cameras that do not have light metering built-in. They are also used to measure flash power when using strobe lighting.

Accurate light readings are essential for setting a correct exposure. A correct exposure is the one that gets your photo looking how you want it to. Light meters read the light intensity. A camera’s light meter in manual mode will indicate when the exposure settings are correct or when you need to adjust them. The exposure meter and camera work together to manage the exposure settings in auto-exposure mode.

How Do Exposure Meters Measure Light?

There are two types of light meters and two types of light: in-camera and handheld. In-camera light meters measure reflected light. Hand-held light meters measure both reflected and incident light. 

The reflected light is light that reflects off any surface. Incident light is the light that hits a surface. The type of surface light reflected off will influence how a camera light meter responds. Light reflecting off a light, mid-tone, or dark surface will produce different readings with reflected light meters. Incident light metering is not affected by the color or tone of what you photograph. Incident metering can provide accurate measurement regardless of what you are photographing. 

A handheld light meter can be an expensive and extra piece of photography equipment. These tend to be used mostly by photographers who need flash metering when they are using strobe lighting. I used to use a handheld meter for studio work and when using film. Now flash meters are not so vital for my work as I know the output settings of my studio lights and can manage them without a dedicated flash meter.

Digital photography using flash is made easier because the camera light meter will communicate with the flash. Together they will calculate the exposure settings, flash range, and output. So when using a flash, you usually don’t need a handheld light meter, especially when using a dedicated flash that communicates with your camera.

Sometimes, a handheld light meter will help achieve exposure settings more accurately in very low light. In very flat, low light reflective metering does not provide the best camera settings.

Why is Light Metering Important?

Light metering is important when you want to capture well-exposed images. What is considered to be well exposed is open to discussion. But, without using a light meter, most people will not consistently capture well-exposed photos.

Occasionally I have met photographers who can assess the available light by looking at it. I am reasonably capable of doing it, but my light meter is more accurate. Light changes; it’s not always the same. 

In the morning, the middle of the day, and in the evenings, it’s different. Before sunrise and after sunset, it’s low and flat. Shortly after sunrise and a little prior to sunset, it’s softer than in the middle of the day. With cloudy skies, the brightness of the light can vary depending on the clouds.

The digital light sensor in your camera is limited in the range of tone it can capture in a single exposure. If too much light affects the sensor, the image is overexposed. When too little light enters the camera, the image is underexposed. The right balance of ISO, aperture, and shutter speed must be used to capture a well-exposed photograph. 

How Does the Light Meter Help You Manage the Exposure Settings?

The light meter assists you in choosing the best aperture, ISO, and shutter speed combinations. In manual mode, the light meter displays a graphic that looks like this in most cameras.

The light meter digital display will read zero when you have set your ISO, shutter speed, and aperture well.

The camera will set the exposure controls partially or manage all three in an auto-exposure mode. Using shutter priority, you can set the shutter speeds, and the camera will adjust the aperture according to the light meter. In aperture priority mode, you manage the aperture, and the camera sets the shutter speed automatically. With other modes, the camera adjusts all three settings. These may vary from camera to camera.

The shutter speed, aperture, and ISO settings you chose also have an influence on other aspects of photography. Aperture affects the depth of field. Shutter speed affects any motion you might capture. ISO affects the amount of digital noise in an image.

When the Light Meter Reads Zero is this Always the Best Exposure?

Reflective light reads differently to camera meters than to incident light meters. A camera’s metering system will read how much light enters the camera after reflecting off elements in the frame. Most handheld light meters can read light the same way an in-built light meter evaluates incoming light. A handheld light meter can also read the ambient light incidentally. It can evaluate single or multiple light sources.

In high contrast, light exposure metering is more critical. Measuring light as it reflects off a dark or light surface will produce different readings. An incident light meter reading will show a different result again. This depends somewhat on how the light is falling on a subject and metering modes.

The angled light reflects off a subject, which affects how even the best light meter reads it. Hard light hitting a subject and reflecting into your lens can make a shiny dark subject look white, depending on your exposure settings. 

How Do Light Metering Modes Affect Ambient Light Readings?

Your choice of metering modes has a direct effect on your exposure settings. The main metering modes in cameras are:

• Center-Weighted Metering
• Spot Metering
• Matrix Metering (in Nikon) / Evaluative Metering (in Canon) / Multi (in Sony)

Camera makers use a variety of names for the default internal camera light meter setting. This mode takes multiple readings from across the frame and provides the light meter with an averaged ambient light reading.

Spot metering is when the setting allows the light meter to only read the light from a very small part of the frame. In this mode, you are reading the amount of light reflecting off a very small area.

Regardless of the light source, an averaged reading produces a similar result to a handheld light meter that’s making an incident light reading. This is the default mode for most digital photography. It generally produces acceptable results regardless of the amount of light coming into the camera lens.

Spot meters are used to make a very precise reading of reflected light. Taking photos in hard light using a spot meter is very helpful in determining the best exposure. It’s essential to use a spot meter when making use of the Zone System. A handheld light meter usually comes with spot meters.

Center-weighted light meters are old and used to be the only option in many cameras. This was long before digital photography. This metering mode is useful for reading the amount of light when your main subject fills the middle of your frame.

The best light meters in cameras often include other metering modes. The three I have covered here are the most common modes on in-camera light meters.

What is the Most Important Aspect of Using a Light Meter in Photography?

A built-in light meter works by reading the light falling on a subject that reflects into the camera lens. The amount of this reflective light depends on the light source and the surfaces it reflects off. 

You may wonder how light metering can accurately read reflective light if the surface tone has such influence. A light meter works on the premise that everything light reflects off is 18% gray. This is the tone halfway between black and white. It’s also known as middle gray. Light falling on any other tone produces inaccurate light metering.

Because light meters are calibrated in this manner, they are consistent in the readings they provide. But this also means when you take a reading from a white subject, it will render as middle gray. This is if you set your exposure settings according to the light meter. When you take a light meter reading from an entirely black subject, the same will happen.

Does the Light Meter Always Need to Read Zero for a Good Exposure?

No! The light meters do not always need to read zero to capture a well-exposed photo. A good exposure depends a lot on the light, the subject, and your intent.

In hard light and in soft light, exposure meters respond differently. While photographing high and low contrast subjects, light meters produce a variety of readings. Having a good understanding of the tone range and the light quality will help you make better choices when exposing your photos.

A relatively low contrast scene in flat light will be well exposed when you adjust exposure settings, so the light meter reads zero. In a high contrast scene with hard light, a zeroed reading might give you a disappointing result, depending on what your intent is for the photo. 

Here’s a short video that will help you understand this better:

Understanding the Zone System will help you achieve more creative exposure. This system helps you understand the tone range and manage your exposure settings.

What’s the Best Way to Use a Light Meter?

I find the best way to use a light meter is as a guide. Use it to gain an understanding of the light and tone range in a scene. Then make your own choices as to how you want your exposures to look. This does take practice. But when you get used to using a light meter in this manner, your photography can certainly become much more creative. 

You will start to see the light and tone in different ways. You will realize that the photos you take do not all need to be exposed generically and look bland. This is what happens when you use averaged metering and an auto-exposure setting.

Take time and experiment. Study how to do this well. In my 365 Days of Photography Course, I concentrate many of the lessons on teaching how to achieve the best use of your light meter.