Lesson 24: Metering Modes

Metering Modes

Metering modes are one of the less flashy, but more vital components to consider for a proper exposure. How the camera meters the light is essential whether you’re using auto/priority modes or full manual and have an effect whether you’re shooting with a DSLR or mirrorless with live view.

The metering modes are how the light meter within the camera biases it’s reading and can make getting the correct exposure much easier once you know how they all work. For the basics though, each metering mode balances the exposure based on what part of the frame is deemed “most important” and will adjust any auto or priority modes based on that reading. There is also a meter either on the bottom or side of the viewfinder (or display) that shows where the exposure will be, with “0” (or neutral) being centered and positive (overexposed) and negative (underexposed) to either side. Usually, this meter also tells you how many stops over or under exposed the image will be.

Standard

While cameras now come with multiple modes, most still have the basic metering of measuring all the light in the scene. This mode, while it has different names depending on the camera manufacturer, has no bias or interpretation and simply reads the light from the full scene. Everything is averaged out, and any calculations on brightness are based on the overall light across the entire frame.

Matrix/Evaluative

In this mode, the camera is still evaluating brightness across the frame but is also judging the scene based on where those bright and dark areas are. It will make a decision based on how the frame is arrayed as to what it thinks is the best exposure for the type of scene you’re shooting. For the most part this mode is fairly effective, it’s becoming the default on many cameras, and will give fairly consistent results for most photography. Matrix mode still evaluates brightness across the entire frame but will bias any priority modes based on where the brightest and darkest parts are.  So, if you have a really bright sky taking up most of the frame but the subject is in shadow, such as for backlit portraits, it will suggest the exposure to keep the subject visible instead of just an average.

Center Weighted

Center-weighted metering focuses on the light just from the middle of the frame. While this can be problematic for landscapes, where the areas you want brightest aren’t usually centered, it can be incredibly helpful for faster paced genres where you want the subject exposed properly and the background is less important. This is also a great mode if you plan to use the Auto Exposure Lock (AE-L) while shooting. This will let you provide the camera with a specific input for exposure and then recompose the image without the camera changing settings on you.

Spot

This mode is best used with smaller subjects, distinct differences between bright and dark areas, and is perfect when using AE-L. It’s similar to center-weighted metering, but even more focused on a smaller area within the frame. This allows you to specify an exact point to measure for brightness and leaves less guesswork to the camera.

Highlight

Some cameras have a highlight priority mode, which focuses entirely on protecting the highlights in your image. This can be useful for landscapes, studio work, or any other shots where retaining as much highlight information as possible is needed. And while incredibly useful for protecting highlights, in highly dynamic scenes this can also lead to loss of detail in the shadows.

Selenium Cell

So far, we have discussed metering modes on modern cameras. For older cameras there are also a few variations, but they essentially function the same as the selenium cell, so that’s what we will cover. Selenium is a light sensitive mineral that produces an electric current dependent on the amount of light that hits it. Because the fluctuation in the current is constant to the amount of light it's exposed to, this allows the camera to give a reading based on the available light even for cameras that have no electrical components. The issue that can arise it that it’s dependent on the light hitting the camera, not the scene. If you are standing in brighter light while your subject is in a shaded area the meter reading will give you an underexposed frame, or vice-versa if you’re in the shade and your subject is in brighter light.

Handheld Light Meters

While all modern cameras, and most functioning film cameras, have some sort of light meter built in there are also handheld light meters available. While these are mostly irrelevant to modern photography it can still be important to understand their function.

Incident Readings

Incident metering is how the selenium meter functions and is more useful off-camera than it is on-camera. Having a handheld meter allows you to measure the light at the subject, instead of at the camera. This is incredibly useful in portraiture where you’re trying to meter off the subject’s face, as it doesn’t matter how the rest of the scene is lit if you take the reading from where the subject will be standing.

Spot Readings

This functions the same as spot metering in-camera, where the meter looks at the light from a specific point in the scene to determine the optimal exposure.

Flash

Some (more expensive) handheld meters allow incident readings based on the output of strobes or flash. This can be helpful even with modern gear as it can eliminate test shots to dial in exposure. While not essential if you’re using a digital camera, for using strobes with analog gear it is absolutely needed if you don’t have a digital camera available to dial in exposure.

Metering in Manual

While metering modes will adjust settings for you if you’re in an auto or priority mode, it will still give you a reading even if you’re shooting fully manual. While it doesn’t change any of your settings, it will give you an estimate of whether your shot will be over or under exposed before you press the shutter. With a DSLR this will be the only way you have to monitor exposure when looking through the optical viewfinder, so knowing how your camera is metering the scene is incredibly important.

With mirrorless cameras, or when using the live feed on the back screen of a DSLR, you will get a preview of the scene but depending on the screen’s brightness and the ambient light it can give a false sense of the exposure. Knowing the metering mode can still help with ensuring the screen’s brightness isn’t giving you a false sense of brightness as you shoot.

Exposure Compensation

When using auto or a priority mode, you can also use the exposure compensation dial to fine tune how the final image will turn out. This can be either a physical dial or a function button that allows you to adjust whether the camera will intentionally over or under expose based on the meter’s reading.

This is useful for when the camera isn’t getting the exact exposure you’d like, but there are still too many changing variables to go fully manual. It can also be useful in a priority mode just to fit consistently with your preferred style.

Reading your Histogram

One feature of mirrorless cameras (and some DSLRs in live view) is the ability to see the histogram before you take a shot. Although the histogram is generally a feature used while editing, if you have access to it while shooting it can be a useful tool to judge your exposure prior to shooting.

The far right of the histogram is the white point while the far left is the black point, and the vertical axis shows how many pixels are at that brightness level. Just like with adjusting exposure in post, adjustments in camera will affect how the histogram looks. If you overexpose, the lines of the histogram will be pressed against the far right. If underexposed, they will be at the far left.

Sometimes though, you will want a mostly under or overexposed shot. The histogram will look unbalanced but can be helpful for figuring out exactly what’s going on. For example, with a low-key portrait the majority of the photo will be dark or completely black. If the histogram shows the largest grouping in the middle, then there may be an issue with keeping light off the background. And for a high-key photo, a “balanced” histogram can indicate that there isn’t enough light on the background. Using this to help dial in a photo before you press the shutter can speed up your workflow considerably without relying on finding out in post how bright or dark your shot really is.

For cameras that don’t have a live histogram, this is another area where spot metering will shine. It can allow for proper exposure on your subject while ignoring the areas you want intentionally bright or dark.

Conclusion

Each of these metering modes has its benefits, and each its limitations. The key to using them is the intention with the style you shoot with and the context of the scene you’re in. You may find yourself using primarily one mode for the majority of your work but having the knowledge of when to change modes can help with difficult lighting, unusual conditions, or even simply trying something new and finding the most effective way to capture it.