The goal of this article is to help you understand camera metering modes so you can take control of your exposure and get the results you want.
What Is Camera Metering?
Metering is when a digital camera measure the amount of light falling onto a scene and compare those levels to a mid-grey (around 18% grey) tone. From there the camera calculates what shutter speed and aperture settings are required to make an exposure which matches this tone.
Once upon a time….
Many years ago, when film was all the rage, metering was something the photographer did, not the camera. You might have owned a light meter, measuring the scene and setting your aperture and shutter speed manually. More likely, you used experience to judge what you were seeing, and helpful guidelines like the ‘Sunny 16’ rule. This required a degree of arithmetical gymnastics to calculate shutter speeds and apertures – something that’ll be unfamiliar to many modern day photographers.
Today we live in a land of luxury, with cameras that have built-in light meters. Most of us take this for granted, but it still pays to understand how metering works. This will help you get the best out of your camera.
Problems with Camera Metering
If you happen to be photographing a scene that’s evenly lit and mostly made up of mid-tones you’re likely to end up with a well-exposed image. Of course, not all pictures are like that.
Try shooting something with big contrasts of light and dark (sunset or snow) and you may not fare so well! This is when it pays to understand camera metering modes so you can take control.
Camera Metering Modes
Modern cameras allow the user to select which part of the scene to be used for calculating the exposure. Thus, knowing which metering mode to use when allows you to take creative control of your exposure.
Let’s explore different metering modes first. Then we’ll take a look at situations where you might want to use them.
1. Evaluative or Matrix Metering Mode
In evaluative metering mode, The camera’s processor divides the entire scene up into zones and analyses the illumination in each one. It then sets an exposure based on the average of these zones.
This tends to be the default for cameras when they leave the factory.
Some manufacturers also compare the scene with a database of images, analyzing which is closest to the contents of the viewfinder. And all of this happens in just a fraction of a second!
2. Centre-weighted metering
This mode works on the premise that most people place the subject of their photo in the center of the frame.
Like Evaluative/Matrix metering, it analyses the whole scene but places more emphasis on the illumination of the central portion of the frame. The size of this central zone varies between different cameras, but it can be anything up to 75% of the frame.
3. Spot Metering Mode
As the name suggests, the camera meters from just a tiny area of the frame, somewhere between 3 and 5%.
On many cameras, this metering zone is always in the center of the frame. But some models will tie it to the active focus point so you can meter off-center.
Some base-level camera models don’t have a spot metering mode, but instead, offer Partial metering. This works in much the same way, but the metering zone will be larger, perhaps 10-15% of the frame.
How to Change Camera Metering Mode
As with the names of the metering modes, how to change your metering mode will depend on the brand of camera you’re using.
Generally, you can press the metering mode button (often a circle in a rectangle) and then use the main dial or cursor buttons to make your selection. If you can’t locate it, grab your camera’s user manual and look up metering modes.
You can also set the metering mode via the LCD panel of your camera. Look for the metering icon and click on it to switch metering modes.
Pro Tip: download the manual for your camera in PDF format and store it on your smartphone or tablet for easy reference.
Which Metering Mode to Use When?
I still shoot most of my images in Evaluative/Matrix mode. However, there are times when this default metering mode fails to correctly expose photos. Let’s look at when to use which metering mode.
1. When to Use Evaluative/Matrix Mode
This is a good, all-round choice for many situations. If you are photographing a scene that’s evenly lit and contains mostly mid-tones, it’ll work beautifully.
For instance, in this landscape, the expanse of greenery is evenly lit and the sky isn’t too bright. Here Evaluative/Matrix metering would be a good choice. If the sky had been much brighter it might have skewed the exposure, leading the camera to underexpose the foreground.
Below is another example of a photo where Evaluative/Matrix metering works well. Although I shot this on a sunny day, the tones of the background and the bird’s plumage are well matched, so the camera averaged things out to create a good exposure. There are small areas of white in the scene, but they are minimal so they didn’t mislead the camera.
2. When to Use Centre-Weighted Metering
This can be a great choice if your subject is in the center of the frame and you want your camera to choose settings to expose it well. For instance, you might be shooting a portrait against a paler background.
Here the model is quite large in the frame and centrally placed. By selecting Centre-Weighted metering, the camera pays less attention to the bright areas around the edge of the frame and calculates a good exposure from the model instead.
3. When to Use Spot metering
Spot metering is really useful in situations where you are faced with high levels of contrast. This could be an occasion where the background is much lighter or darker than the main subject, especially if the subject of your photo is relatively small in the picture.
For instance, in below image, the area of the man’s face we want to see in detail is really quite small.
Faced with that large expanse of darkness, Evaluative/Matrix mode would expose the scene to be 18% grey. This would wash out those black tones and the man’s face would be horribly overexposed.
By selecting Spot Metering and taking a reading directly off his face, you tell the camera this is the area you want well exposed. It then ignores the rest of the scene and the resulting image is much more impactful.
Using Auto Exposure Lock in Spot Metering Mode
As I’ve already mentioned, the spot metering area in some cameras is fixed in the center of the frame. This is great if your chosen subject is central to your picture. However, sometimes a composition works better when the subject is placed to one side, or at the edge of the frame.
Why should I use AE-Lock?
If you used spot metering on this picture the exposure would be made from the white background. Because our cameras are designed to expose everything to a medium grey tone, the resulting image would be darker than is desirable. If your camera’s spot focus zone is locked in the center of the frame you can still take control by using Auto Exposure Lock, or AE- Lock.
How to use AE-Lock?
- Place the center metering zone over the subject you wish to be well exposed – in this case, the apples.
- While half-pressing the shutter button, also press the AE-Lock button on the back of your camera.
- This locks in the exposure to your subject.
- You can now go ahead and recompose your picture, with your subject off-center, and shoot. Simple!
Taking Control Using Exposure Compensation
As you already know, my most commonly chosen metering mode is Evaluative/Matrix. It often works really well, but there are occasions when I need to take control. I do this by using Exposure Compensation.
For instance, if I’m shooting a scene that’s predominantly dark, the camera will try to brighten the image to make everything comparable to an 18% grey tone.
When I photographed this Harris Hawk, I knew the dark background would fool my camera’s metering system to overexpose my image. I, therefore, dialed in some negative exposure compensation – minus one stop. This told the camera to lower the exposure, making the scene darker than it would otherwise have done.
At the other extreme, very bright scenes can also confuse your camera’s metering system. For instance, a snowy landscape will contain lots of bright tones. Left to its own devices, your camera will darken these shades of white to mid-grey.
We all know that snow should be white so grey snow just doesn’t look right! Instead, you need to dial in some positive exposure compensation, perhaps one stop or more, to compensate for this underexposure.
Over to You
Hopefully, this will have helped you unravel some of the mysteries of metering in photography. My aim here is to let you take control of your photos, rather than your camera bossing you about! Why not get out there now and take the various metering modes for a spin?
Try shooting a picture in all the different metering modes and see what difference it makes. We would love to see some of your photos or questions in the comment section below!
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