Light metering modes: One simple question


Firstly I’d like to apologise for the lack of tutorial last week, I was in the remote village of Tufi in Papua New Guinea with very little time and only satellite internet. During this stay though we had a few visitors one afternoon from a very swanky and exclusive cruise ship. As the sun started to set they raised their incredibly expensive cameras in unison and snapped away at the sun dipping below the mountains in the fiord. Sitting back watching, I noticed some tremendously mixed reactions, some lit up with glee and others cursed at their images like they might a puppy who relieved itself on the rug. But let’s face it, the problem wasn’t the camerea getting it wrong. So this week in my tutorial I’d like to welcome you to the world of light metering, the single setting that can make or break your photos and the one question you need to ask yourself before selecting a metering mode.

First, what is light metering? Essentially it’s the part of the camera that measures the incoming light and determines how bright a scene should be in the end photograph. There are three general types of light metering modes, evaluative, centre weighted average and spot metering. These three modes each look at different parts or combinations of parts of the image to determine how to adjust the brightness. The tricky part about getting the brightness of your image right is that when we look at different subjects our eyes constantly adjust depending on the subjects brightness. For example, if I stare into a dark room, my eyes will (eventually) adjust to make the room seem brighter and if I’m in a bright situation my eyes will adjust to darken the scene to be more comfortable for my viewing. The camera in any of the ‘automatic modes’ (Program, Aperture Priority, Shutter Priority) are trying to replicate this experience. So what happens when I look at a scene that has both bright lights and dark shadows?
Let’s have a look at the image below.

Edited final image

If you look at a sun setting in front of you with dark silhouetted mountains and reflections popping off the water and I asked you ‘how bright is this scene?’ you might struggle a little bit to answer that question because there are dark parts AND there are bright parts. So do you kind of just average them out or do you pick one part of the scene to adjust your eyes to? This is exactly what the light metering modes are for, and the reason so many of those tourist were cussing at their camera, they were simply asking the camera to base it’s calculations on the wrong part of the image.

Evaluative/Matrix Metering – Correct for this situation

In the first image (below) the camera was set to Evaluative (or Matrix depending on your camera brand). This means that the camera looks at the whole scene, the shadows, mids and highlights, averaging them out to give you a balanced look across your whole scene.

Centre Weighted Average Metering

The second image (below) is centre weighted, where the camera looks at the centre spot and then includes the immediately surrounding area. As you can see, it is now looking mostly at the darker mountains and trying to brighten them up because that’s what it believes is your subject.

Spot Metering

The final image (below) is spot metering where the camera only looks at the centre spot of your frame (some cameras will move the metering spot with the focus point). Agin this lands the light metering on the mountain causing the camera to adjust it’s brightness (like your eye would) based only on the mountain.

So if spot and centre weighted metering modes give me these terrible results for landscapes why or when would I use them?

Spot Metering

Because I am only concerned about the girls face, I set to spot and ensure my centre spot is on her face when I half press the shutter button.

Centre Weighted Average

I don’t really care about the far sky background but I want the brightness to be correct for the child in the middle as well as taking into account the other kids who are in slightly more shadow.

The easiest way to choose which mode to use?

Think about the red shapes on the first images as the ‘answers’ to this question:
“What is your subject?”

Spot metering is used when the subject is a particular thing (think portrait, object etc), evaluative is when your subject encompasses the entire frame, for instance a landscape or seascape and centre weighted is when your subject is defined but you are also wanting to keep the surroundings of your main subject as a feature as well. Learnt something in this tutorial? Join me on a workshop or day trip! And don’t forget to subscribe to my weekly tutorial below!

Tip: If you are new to photography, start by using only evaluative as it is the safest mode. If you use Spot metering mode, be sure the centre spot is on your subject when you lock focus by half pressing the shutter., This will generally also lock the brightness and your subject will come out looking great!

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