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Light meters

Have you ever struggled to get the perfect exposure in your photos? Maybe you've tried adjusting your camera settings, but you just can't seem to get it quite right.

That's where a light meter comes in...


What is a light meter?

The light meter is a device that can read the ambient light of a scene, it can also measure the direct light coming from your main light source. Simply by looking at the name, you can easily discern that a light meter measures light.

You will usually see professional photographers bring out a little “walky-talky-ish” device, yeah those are the external versions of a light meter.

Light meter on a desk.
My light meter

A light meter isn’t always a separate device, most photographers just prefer the external version. Your camera has a light meter built-in, sometimes called the exposure meter, but it only measures reflective light.

Exposure meter on a camera.
Exposure meter on camera

As a device that is essential to measure how bright a “spot” is, photographers tend to hover on the most detailed one. The camera's version of a light meter solely measures the reflected light, which is pretty problematic. Since cameras try to compensate exposures when set into an automatic or semi-automatic mode, it will most likely not result in the image you have in your mind.

Other than measuring light there are some other neat features. For example, the Sekonic L 308X U is able to determine the aperture, shutter speed, measure your flash, measure reflective light, and change the ISO, and also comes with various modes. This versatility and abundance of features make it a must-have for photographers.


What does a light meter do?

So, what does a light meter do? Photographers who prefer to shoot indoors or in studios will also use this device to calculate the correct shutter speed and aperture values that they need to acquire accurate exposure of their subject or object.

Although you can also use this device for shooting outdoors, it will most likely be a waste of time and will be inappropriate for certain venues. For example, when shooting at outdoor venues such as weddings, birthday parties, or even meetings.

Take note!

It will become simply inefficient to move back and forth between your spot and the subject to just measure the light.

Personally, I just use what’s available and adjust my aperture and shutter speed. Unless I’m there to take a commercial shot and must take a few stunning shots. It will also calculate the required shutter speed and aperture to match your desired exposure for a shot. No matter if you shoot in manual, aperture mode, or shutter priority mode, this handy light meter will always have your back.


How to use a light meter

1. Understand the basics of your light meter

The first step in order to use your light meter, is to first understand the basics of this photography tool. The three main parts you need to know about your light meter are its sensor, measurement display, and controls.

Sensor

The sensor in your light meter is responsible for measuring the intensity of light. It captures the light that falls on it and converts it into an electrical signal, which is then used to calculate the appropriate exposure settings.

Your sensor's sensitivity can be adjusted based on the ISO setting, ensuring accurate readings across different lighting conditions.

Light meter with an arrow pointing to the sensor.
Sensor on light meter

Measurement display

The measurement display is where you view the exposure readings provided by the light meter. The display will typically show the recommended shutter speed and aperture values for proper exposure. I wanted to also note that some light meters also display an EV (Exposure Value) reading which just represents a standardized exposure measurement.

Light meter with an arrow pointing to the measurement display.
Measurement display on light meter

Controls

Lastly, light meters come equipped with various controls to adjust your settings. These controls could include buttons, dials, touchscreen interfaces, etc. - depending on your brand and quality of light meter, with the more expensive ones having more "bells and whistles."

Light meter with an arrow pointing to the controls.
Controls on light meter

The common settings you will be adjusting on your light meter include the ISO, metering modes, exposure compensation, and metering area size. Since you will be adjusting these settings, it's important you know what each of these terms means so be sure to check out the guides we have on each term!

When I first started using a light meter, I knew understanding its components was crucial to becoming proficient with exposure control. I remember getting my hands on a handheld light meter with a digital display. I took the time to examine the device closely, noting the presence of a small sensor located on the top panel, taking time to explore the backlit LCD screen measurement display, and navigating through the different controls.

The biggest tip I give photographers is to just take time to familiarize yourself with the different components and functions. From there you will gain confidence in using your light meter!

2. Learn the metering modes

The second step is to learn the different metering modes. Why you may ask? Well because metering modes play a crucial role in determining how your light meter will measure light and provide exposure recommendations.

The three main metering modes you should know include spot metering, center-weighted metering, and matrix/evaluative metering.

Different metering modes.
Different metering modes

Spot metering

Spot metering measures light from a small, specific area of the scene which is great for precise exposure control for a particular subject in your frame. When using spot metering, the light meter concentrates on the selected area, providing exposure recommendations based solely on that spot.

For example, one time during a portrait session, I wanted to ensure accurate exposure for my model's face while maintaining the desired background exposure. By using spot metering, I aimed the light meter at the model's face, specifically measuring the light falling on her skin.

This allowed me to obtain a proper exposure for her complexion, disregarding the brighter or darker areas of the background.

Center-weighted metering

Center-weighted metering evaluates the light primarily in the center portion of your frame, giving more importance to the exposure around the center. You'll want to use this mode when the subject is centrally positioned or when you want to balance the exposure of your main subject with your overall scene. For example, if you take a landscape photo with some mountains in the center, you may want to use center-weighted metering.

If you do so, the light meter will consider the exposure around the center (the mountains), ensuring they are properly exposed while also taking into account the surrounding elements.

Matrix/Evaluative metering

Matrix or evaluative metering (depending on your camera brand) will evaluate the light from across the entire frame and consider multiple areas and factors.

With that being said, your light meter will evaluate multiple elements such as the brightness, contrast, and color distribution in your scene in order to try and provide the best exposure recommendations. This mode is great if you are photographing in diverse lighting scenarios.

3. Set your ISO

The third step when using your light meter is to set your ISO. Setting your ISO will ensure that both your light meter and camera are calibrated to the same sensitivity. In case you need a quick recap, the ISO refers to the sensitivity of your camera's image sensor to light.

Because of this, it's important to match the ISO on your light meter to your camera so there is exposure consistency.

For example, during a photo shoot in a dimly lit environment, I set the ISO on my camera to 1600 to increase its sensitivity to light. However, I initially forgot to adjust the ISO setting on my light meter, which was still set to the previous shoot's ISO of 400.As I started taking exposure readings with the light meter, I noticed significant discrepancies in the recommended shutter speed and aperture values (the other two components of the exposure triangle). The meter was suggesting significantly longer exposures than I anticipated. Realizing the oversight, I quickly adjusted the ISO setting on the light meter to match my camera's ISO of 1600.

4. Ambient light measurement

Ambient light is generally referred to as the existing natural light in the scene such as light coming through a window. When using a light meter, it's up to you whether you want to measure the ambient light or the light falling on your subject (known as incident light).

5. Meter reading

The fifth step is to point the light meter toward the subject or scene and get a reading. This step is fairly straightforward and consists of you aiming your light meter toward your subject or scene (based on the previous step discussed), activating the metering function, analyzing the light, and then looking at the exposure information.

6. Evaluating the meter reading

The sixth step is to evaluate the reading you received. When it comes to evaluating the reading, the first thing you'll want to do is check the exposure values. When your light meter analyzes the light it will display the recommended shutter speed and aperture values. If you metered correctly, then these values should represent the suggested settings to achieve proper exposure in your current scene.

In case you need a quick recap on what shutter speed and aperture is, here you go:

  • Shutter speed is responsible for controlling the duration for which your camera's shutter remains open. The faster the shutter speed (ex. 1/1000s) then the less light will pass through and vice versa.
  • Aperture, on the other hand, controls the size of your camera's lens opening, impacting the amount of light that enters the camera. For example, a wider aperture (lower f-stop value such as f/1.8) will allow more light to enter.

Once you receive your shutter speed and aperture value, you will then need to consider the creative choices you want to have in your photo.

For example:

Capturing motion blur in an image will require a slower shutter speed, or capturing a wide depth-of-field image with bokeh will require a wider aperture.

It's important to know what creative outcome you want to achieve so you can better tweak the exposure settings once you receive your reading.

7. Adjust your camera settings

The seventh step is to adjust your camera settings based on everything discussed in the previous step. Once you receive your exposure settings and know what creative choice you want to have in your image, adjust your camera to those settings.

8. Take test shots

The eighth step is to start capturing some test shots. Once you've adjusted your camera settings based on the reading from your light meter, you'll want to capture a few test shots using the suggested settings to make sure everything looks good.

This will allow you to evaluate the initial results based on the suggested settings, review the images, and make any necessary adjustments to fine-tune the exposure.

9. Fine-tune

The ninth step is to fine-tune your settings. If the test shots indicate overexposure or underexposure, it's important to make adjustments to the exposure settings, such as the aperture, shutter speed, or ISO.

This iterative process allows you to refine the exposure until you achieve the desired result.

Tip:

Think of this whole process as a loop where you capture a reading, evaluate the reading, adjust your camera settings, take test shots, and then fine-tune.

If you don't like how the images look then go through the loop again.

10. Recalibration

The tenth and final step is recalibration. If you notice your readings are starting to get way off, then you may want to compare its readings to other light meters to make sure that your light meter is still working optimally.

If you notice significant discrepancies, I'd recommend you to recalibrate or service your light meter.


How do you read a light meter?

To measure the light in the first place and use your light meter, you put your dome on your subject and face it to your main light source. It will then show how bright it is in increments of f-stops.

We do have single articles that explain the basics of each of these elements, I highly recommend you read those articles. For now, I’ll just explain the concepts in a nutshell:

  • ISO: ISO is essentially how sensitive your camera’s sensor is to light. Higher ISO will make it more sensitive, thus allowing you to take brighter pictures in low-light situations and vice versa. Most cameras will not emit noise if you use a 3200 ISO, but each camera is different.
  • Shutter Speed: Brutally oversimplifying it, shutter speed is how fast your shutter can close and open again. The longer/slower it gets to close, the lighter it lets in, which allows more light to hit your camera’s sensor. A Longer Shutter speed translates into a brighter picture and vice versa. But, since it’s slower to close moving objects or your shaking hands will make the image blur.
  • Aperture: This controls your lens focus plane. A smaller aperture (f/32, f/16, and f/8) will give you a thorough focus on the scene. On the other hand, a larger aperture (f/1.4, f/2.0, and f/2.8) will focus on the foreground and blur out the background. Larger apertures will also make the image brighter since more light can enter the camera's sensor and vice versa.

Is a light meter necessary?

Light meter photography will help you achieve that perfect shot every time. Without a light meter, you’ll go back and forth from shooting a photo, reviewing it, and taking it again, until you get a satisfactory photo.

Some argue that taking a shot and quickly reviewing them manually will be quicker than pacing around while measuring each light source. I would argue that the efficiency of each method would be different depending on your location and venue.

Portrait photographers that shoot multiple sessions of graduation images would love to have a reference for their exposure triangle.

For you creative people out there, the light meter can be portrayed as a threat to your creativity. Using a light meter gives you optimal and perfect exposure. But perfect is not always welcomed, perfect does not tell much of a story, and a perfectly exposed image doesn’t make it automatically fulfill your theme/idea.

I think that you can still use them regardless, you definitely should not fully rely on them and let them determine your exposure. A light meter will provide you with information that can help you easily review and recreate the image! The more data that you have when documenting your artwork, the easier it becomes to recreate it in the future.

This item becomes a valuable part of the amateur photographers' learning process. Use everything you have to help you learn and as time goes on you’ll naturally part ways from it.


Are light meters accurate?

Well, it depends on the light meter you’re talking about. Most external light meters are as accurate as you use them. On the other hand, light meters that are built-in aren’t so accurate.

  1. First of all, a camera's light meter will only measure reflective light that’s from the subject and doesn’t measure how bright the light source is.
  2. Secondly, the light meter on your camera tends to give you results after color compensation. Color compensation is your camera adjusting the current exposure based on the 18% grey area, most of the time it underexposes/overexposes the image.

These two factors are the main argument for why people say that built-in light meters aren’t accurate. Your external light meter will probably do a better job at measuring reflective light than your camera. If you use them properly, every light meter can be an extremely accurate one.


What to look for in a good light meter?

When choosing a good external light meter, look for one with diverse metering modes including incident and spot metering to provide accuracy across different shooting conditions, and ensure it offers features like high sensitivity for low light scenarios and flash metering capabilities. Additionally, consider a user-friendly interface with options for calibration to match specific camera systems and conditions, enhancing both ease of use and precision in exposure settings.


In conclusion, a light meter is an instrument that helps you measure light. It provides you with an accurate combination of Aperture, Shutter Speed, and ISO. Besides that, it is also handy at helping you recreate previous photos or light setups. Some like the instrument, while others prefer to stay away from it.

I see a light meter as a tool to assist photo sessions that need precision and fabulous shots. Some also use it as a stepping stone before entering manual mode. The more experiments and situations you go through with this instrument, the faster you’ll recognize situations where it’s less effective.

Good luck and have fun!

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