What is a Light Meter? | Photography Definition and Tips

This is a guide covering light meters.

In this glossary definition you’ll learn about:

Have you ever imagined a device that measures and gives you accurate settings for your desired exposure? Well, it exists and is called a light meter.

Let’s dive in.

light meter

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.

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

As a device that is essential to measure how bright a “spot” is, photographers tend to hover at 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 aperture, shutter speed, measure your flash, measure reflective light, 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 it 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 the 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. 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.

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, taking it again, until you get a satisfactory photo.

And just like an AD would go, this light meter will solve your problems in one go. The meter displays the required aperture and shutter speed that you are recommended to set after the light has been captured.

The light meter definition sounds too good already, how does it get even better? Well, that is where I must warn you about the debating climate between “light meter converts” and those who oppose them.

I would like to disclaim that both parties have their points, and their arguments are also strong.

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 fulfil your theme/idea.

I think that you can still use them regardless, you definitely should not fully rely on them and let it determine your exposure. A light meter will provide you with information that can help you to 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. Using everything you have to help you learn and as time goes on you’ll naturally part ways from it.

purpose of key light

How Do You Read a Light Meter?

To measure the light in the first place, 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.

Each stop is twice or half as bright respectively based on a stop higher or lower than it. Meaning that an f/2.0 is twice as bright as f/1.4.

On the popular Sekonic Light Meter 308s that everyone uses, there are three readings: ISO, Shutter Speed and Aperture.

ISO on the top right, located below it is the Aperture, and on the bottom left is your shutter speed. That’s all the big three settings that you’ll need to know when reading your light meter.

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. 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.
studio light meter

But did you know that you can use your light meter to essentially count your desired setting that you want it to? Because it can. Changing the aperture will make your shutter speed slower or faster depending on how you change it. Choosing a smaller aperture will, in turn, make your shutter speed slower too.

The light meter is basically compensating for the apertures exposure by making the shutter speed slower. But what if your hands are shaky?

Well, in this case, you can simply bring out the Tripod and attach a wireless remote shutter release on your camera. In case you want a faster shutter speed, you can just increase the ISO by pressing the ISO setting on the side and push it up.

Your Aperture and shutter speed will naturally rise too since all elements are connected to each other, but don’t worry you just need to lower your aperture back, and voila! A faster shutter speed, same desired aperture, at a higher ISO.

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.

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.

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 times 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.

measuring light
Photo by Luis Dalvan

What to Look for in a Good Light Meter?

I must say that your purpose is one of the leading factors that you should consider when purchasing your light meter. There are many options to consider in light meter photography, starting from the type of light meter, the various features that it has, and also your preferred manufacturer.

There are three main types of light meters:

  • Incident Light Metering: This determines the exposure based on the light that falls on the subject. It also provides a quick estimate of exposure for multiple light sources.
  • Reflected Light Spot Metering: This refers to the light that is reflected by the photographed environment.
  • Flash Metering: With most flashes lasting a 1/1000-second, most capable flashes have a PC terminal or other sync port for the triggering of a flash. There are also the dedicated mode that puts your meter on standby and will capture and save the measurements when the flash is triggered.

There are also various utilities and functions that you should consider which are (but is not limited to):

  • Data Entering: This will help you download test images into your computer, from RAW into TIFF. The data transfer will also help you graph any DSLR cameras dynamic range.
  • Spot Viewfinder: This feature helps you in making correct exposure choices with its large, information-packed data display and viewfinder equipped with a diopter correction.
  • Memory Mode and Latitude Display: This mirrors your camera’s dynamic range which aids you in deciding over the exposure settings.

Manufacturers only matter if you already have a pre-existing bond and personally know how good their products are. Some famous light meter manufacturers are Sekonic, Phottix, Nikon, and Canon.

Final Remarks

So, what is a light meter? It’s 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 setup. 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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