Equipment Essentials: What Is a Light Meter in Photography?

To get a perfect exposure, light meters are nearly essential for photography. True, some very experienced photographers can guess the exposure values for a given scene based on past experience and knowledge of the intricacies of light.

However, for the vast majority of us, a light meter is needed to help us figure out exactly how much light is falling on our scene and how to adjust aperture, shutter speed and ISO to capture an even tone. Light meters come in a few different forms and can be used in different ways. Read on to learn more about light meters in photography!

The view from an in-camera light meter

What is a light meter in photography?

Typically, you will want to see a variety of tones in an image. You’ll want to see highlights, shadows and a range in between. The light meter is used to find that place where you get the greatest range of tones. It measures the amount of light that will be hitting your sensor so you know you are not underexposing or overexposing the important parts of your composition.

How do you use a light meter?

There are two ways to measure the light: reflected and incident. Your DSLR measures reflected light. The light source hits your subject and is reflected from the subject toward your camera. The amount of light reflected is metered in camera and if you are using an automatic mode, it is automatically calculated into a shutter speed and f-stop value.

A handheld meter can measure reflected light, but it can also measure incident light. To use it for incident light you would place it near the subject and point it toward the camera. This can be a more accurate reading because it measures the light directly from the source, rather than a reflection of the source. Incident meters are also more helpful than reflected when you are working with flash because it can calculate the intensity of the flash and tell you the correct shutter speed and f-stop values for your photo.

This is a tricky lighting situation where knowing how your light meter works is invaluable.

Types of light meters


Using an in-camera light meter is great because it’s always there with you and can be very accurate if you know how to use it. There are typically three modes to the in-camera meter: spot, center-weighted and evaluative. Spot metering takes one spot in your frame, usually in the dead center or wherever your focus point is selected, and measures the reflected light on that spot. This is about 3 to 5 percent of your total composition.

This type of metering makes sure that your subject shows up as a midtone. Of course, if your subject is a bright white or dark black color, the metering will be incorrect, but for most subjects this works pretty well. Center-weighted metering uses that same spot as the spot meter, but averages in the tones in the rest of the frame. Evaluative metering takes 100 percent of your frame, averages all of the tones, and makes sure you have a completely even image — not too much highlight or shadow.


Handheld light meterPhoto via Shutterstock/Sergey Novikov

Handheld light meters were necessary in the days of film and before in-camera light meters. With DSLRs, you can see immediately on your LCD screen if the in-camera light meter got it right. With film cameras, the moment was gone and it was days or weeks later before you could see if you got your metering right. So handheld meters took the guesswork out of film exposing and flash lighting.

Nowadays, many film shooters still rely on handheld light meters for perfect exposure to save time and eliminate waste. I could also see how some digital shooters still might value the incident light meter on a handheld meter for studio situations or when there just isn’t enough time for trial-and-error guesswork in tricky lighting situations.


It had been years since I shot film and after writing a recent post on using film for wedding photography, I decided to dabble in it again. My film camera does not have a light meter and I do not have a handheld meter, so I have been using an iPhone app called Pocket Light Meter with decent success. It uses the built-in camera to measure the light and give me a reading based on the ISO rating of the film and the aperture I would like to use.

Light meters do not replace knowledge and experience, but support them. Knowing how your meter works and how the different ways of measuring work will make you a better photographer.

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