When it comes to getting the best image quality from your camera, metering is one of the most crucial ingredients. In this tutorial we explain a series of camera metering techniques designed to give you the most accurate exposure possible.
What you see isn’t always what you get. The human eye copes with high-contrast scenes much better than digital cameras do, so photographic images often have washed-out highlights or lack detail in the shadows.
Most current DSLRs feature systems that can effectively boost dynamic range, such as Canon’s Auto Lighting Optimizer and Nikon’s Active D-Lighting but, even so, there’s no substitute for nailing the correct exposure setting to do full justice to the most important aspects of a scene.
Evaluative metering, also known as Multi-segment or Average metering, is a catch-all mode where the camera’s light metering system takes in the whole frame and makes a best guess at the exposure setting that will give a good balance.
The catch, and it’s a big one, is that a ‘good balance’ is often the last thing you want, because it can make people in backlit portraits look like silhouettes, or dumb down bright white objects to a dingy grey.
For effective metering, one option is to stick with the Evaluative mode and to dial in an appropriate amount of +/-EV (Exposure Value) bias, generally referred to as exposure compensation. For example, in a heavily backlit portrait, you might need to apply between +2EV and +3EV exposure compensation.
The background will most likely be washed out to white, but the all-important skin tones in the portrait should be lively and vibrant, rather than dull and muddy.
At the other end of the scale, when shooting a subject against a very dark background, you will typically need to apply negative exposure compensation to ensure that the main subject is correctly exposed, at the expense of lowlights (which are generally of secondary importance) descending into gloominess.
For greatest accuracy in tricky light, it’s worth switching to a more selective metering mode, like Centre-weighted, Partial or Spot metering.
The Centre-weighted option automatically gives metering prominence to the central region of the frame, taking less account of how bright or dark the scene is towards the sides and corners. Partial and Spot go a step further, completely disregarding everything outside respectively small and tiny areas of the frame.
In any metering mode, and especially in Partial or Spot, it’s vital to make a distinction between ‘accurate’ and ‘good’ metering. Technically, a camera’s in-built light meter sets an exposure that corresponds to the amount of light reflected from an 18% grey card.
This is fine if the subject you’re photographing happens to equate to 18% grey but if, for example, you’re taking a portrait of somebody with fair skin, you’ll still need to add around +0.5EV exposure compensation to avoid the skin tones looking dull and muddy.
Settings for outdoor landscapes are often comparatively straightforward, as green grass typically corresponds very closely with the reflected light value of 18%, usually resulting in wonderfully vibrant scenic shots.
Take full control of your camera’s metering in Manual shooting mode
Many cameras only offer as little as +/-2EV exposure compensation, which often isn’t enough for very tricky lighting conditions. So switch to Manual mode and you can dial in the exact exposure values you want.
Try bracketing your exposures, taking several shots across a spread of EV settings. It’s true that if you shoot in RAW you can adjust the EV at the editing stage but, for the very best quality, you’ll need to be within half a stop of the ideal EV when shooting.
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