Understanding Metering Modes

It doesn’t much matter which make of camera you choose they all offer a variety of ways to measure the light reflected back from your subject and so how the camera sets exposure. Understanding this can be very useful. In class I am often confronted by students who have selected spot metering, without understanding why, because they thought it was more professional. This article, although focussing on Canon cameras explains the use and purpose of metering modes.

Taking a photo is often referred to as ‘making an exposure’. This is because when you press the camera’s shutter release button the mirror that reflects the image into the viewfinder flips up out of the way, allowing the imaging sensor to be exposed to light.

Another sensor inside the camera, called the metering sensor, is central to this whole operation: it measures the light that’s coming through the lens and determines how much is needed to produce a well-exposed photo.

SEE MORE: Metering mode cheat sheet – how they work (and when to use them)

Of course, you can let your camera do everything and hope it produces the goods – and much of the time it will.

However, you’ll often be able to improve things if you get involved in the process, and the first step is to choose the metering mode the camera uses to measure the light.

The majority of Canon EOS cameras have four metering modes: Spot, Partial, Centre-weighted Average and Evaluative, all of which work in the same way.

As light is reflected from a scene or subject through the lens, it hits the mirror in front of the imaging sensor and is reflected up to the camera’s focusing screen and metering sensor.

However, each of these modes takes an exposure reading from a progressively larger part of the frame.

As the name suggests, Spot metering offers the most precise metering – anywhere from 1.5%-10% of the total picture area, depending on the camera – while at the other end of the scale, Evaluative metering takes a series of readings in zones that cover the entire frame.

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