Digital cameras come with built-in light meters. Mostly, they do a good job of reading the light in a scene and helping you judge your exposure settings. But if you want to be absolutely sure of the light and get an accurate exposure, you need to use a handheld light meter. If that sounds intimidating, here is your light meter guide.
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What is a light meter?
A light meter (or exposure meter) is a device that is used by photographers to measure light. Typically, a light meter measures the amount of light in a scene and gives an exposure value (or EV), which you can use to set the camera’s aperture, shutter speed, and ISO value. If you’ve done everything tight, you’ll have a proper exposure.
Most cameras have an internal meter built into them, which gives you that value. If you look inside your viewfinder, this is typically indicated by a little arrow or a number preceded by + or -). Usually, cameras have reflective meters, but there is another type of metering called Incident light metering. Handheld light meters often give you the option to choose which type of light metering, you want to use.
While reflective readings are good, incident light readings are better. We will look at why this is, and how to take incident light readings to help you get a correct exposure.
Reflective light meters
A reflective light meter measures the light reflected by your subject through your lens and into the camera. It then calculates what a good exposure will be using ‘middle grey‘ as its benchmark. In theory, if a scene is at middle grey, it has the right balance of light and dark in it. Of course, that isn’t always the case. Some scenes are lighter or darker than others, and this fools a reflective light meter. Consider, for example, a photo taken at night, which should be dark, or a photo taken in mid-day in a desert, which should be bright. Both of those are not “middle grey”. In these cases, your camera’s light meter will suggest an exposure value that will over- or underexpose your scene. Examples of this include:
- A bride in a white wedding dress.
- When you photograph a dog with a black coat.
- A backlit subject.
- Scenes that are full of contrast or have a bright background.
To make it easy. A light meter assumes that everything is grey. It can’t really know if you aim for highlights or shadows in your frame. If you ever heard of Grey cards, this is where you use them.
With experience, you will learn how to dial in exposure compensation for optimal exposure in these situations. You can also choose a different metering mode in your camera to get a more accurate reading. If you are in doubt, you can always refer to the camera histogram, which is a more refined tool.
A quick aside on camera metering modes
The default metering mode for most cameras reads the light from across the entire scene. Nikon calls this matrix metering. Canon calls it evaluative metering. It works well for landscape photography.
You can select different metering modes, though. Spot metering reads the light from a tiny area of the scene. Center-weighted metering reads the light from the middle of the scene. You might prefer it for some portrait photography.
Or you can set the exposure for the scene using a different type of light metering device.
Incident light meters
An incident meter is a handheld device that measures available light rather than reflected light. Instead of measuring how much light is reflected off a scene, it actually measures how much light is falling onto your scene from all the available light sources. Since you are measuring the amount of light that “hits” a certain place, you need to be able to hold the light meter in that specific place. For example, in front of your subject.
[Geak alert] Internally, the light meter gathers the light that hits its sensor to measure the LUX, or light intensity at a specific spot. (older photographers may remember foot candles as well) It then breaks this value into the right exposure value, picking the right shutter speed, aperture, and ISO values to use.
Some handheld light meters also have a spot metering option. This is good if you are shooting in a studio, for example. You can take spot readings from across the background and adjust your lights to make sure you get even lighting.
Old light meters did not use batteries. Instead they had light sensitive cells that pushed a needle around a dial to give you a reading. You can still buy needle-display light meters but most are battery operated and give digital readouts. You can even download apps that turn your smartphone into a light meter.
How to take a light reading with a handheld exposure meter
Using an incident light meter is quite straightforward. You always tell it the ISO you’re using. Then depending on your camera settings, you get to choose:
- If you want to control your aperture, for example, to ensure a shallow depth of field, you tell it your aperture. It will then tell you what shutter speed to use.
- Or, if you need to control the shutter speed, you dial in that. The light meter will then determine the correct aperture for the exposure.
This means you must use manual mode, aperture priority, or shutter priority mode.
As you need to hold the light meter in front of your subject, it can help to have an assistant, especially if you are using flash.
- Select your camera mode.
- Dial in the ISO to both the camera and light meter.
- Choose either your aperture or shutter speed on your camera and then the light meter.
- Activate your light meter.
- Set it to read for ambient light or flash.
- Hold the light meter in front of your subject with the lumisphere (the white dome) pointing toward your camera. Press the metering button to take a light reading. If you are shooting with flash, you will need to fire the flash at the same time.
- The light meter will tell you the ideal shutter speed or aperture for your scene. Dial these into your camera.
If you are shooting manual flash in the studio, you will find it best to use a handheld light meter. This will give you an accurate light reading so you won’t overexpose your shots. Just remember to fire your flash at the same time that you ask the meter to take a reading.
Some meters, can also measure the quick light burst that strobes produce. In the fast, those were called Flash Meters. Today though, this ability is present in most light meters and is indicated by a small flash sign. Some meters, even have the ability to trigger flashes.
A handheld light meter might sound like a complicated piece of equipment. But if you are used to shooting in manual mode they are very straightforward. They will also ensure that you get a good exposure in tricky lighting conditions. Sure, you might want to stick with your camera’s evaluative meter for landscapes, but for weddings, portraits, or in the studio? Pick up a handheld light meter!
A handheld light meter measures the light in a scene, not reflected light. This makes it much more accurate than a reflective light meter.
Yes! There are several apps which turn your phone into a light meter.
It’s best to use your camera’s meter for landscape photography.
A light meter will take the guess-work out of choosing your settings for flash photography.