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With spot metering, the exposure you get depends where you meter from

METERING modes have made huge advances across recent generations of cameras, with intelligent ‘pattern’ metering systems able to deliver well-exposed images in situations where you’d previously end up simply binning the results. But that’s not to say they’re foolproof. There are still times when the camera meter can struggle to make sense of a subject – such as when you’re shooting in very low light – or where the scene has such a wide range of brightness values that the camera averages out the scene incorrectly.

Although camera manufacturers use different brand names for their metering modes, they’re all designed to measure the level of brightness through the lens, and suggest an exposure – a combination of aperture, shutter speed and ISO – to record this brightness correctly. The meter doesn’t set the exposure per se, as you can manually alter each of the exposure parameters on the camera, but it provides a visual guide to the ‘correct’ exposure via the exposure scale in the

viewfinder and on the rear screen. There are three basic variations of metering mode. Spot-metering and centre-weighted measure different proportions of the scene projected by the lens, and require a good understanding of when and how to compensate for bright or dark areas.

However, the default option, which the camera is set to when it ships from the factory, is pattern metering mode. This is

Although cameras have different brand names for their metering modes, they do the same job

an ‘intelligent’ metering mode that takes multiple meter readings across the scene; it then compares the variation in brightness values before coming up with an exposure level that it determines will give the best result.

This approach essentially applies its own compensation to make a scene brighter or darker so you don’t have to, and can take into account the position,

distance and size of the subject (the area that’s in focus, essentially). Some advanced cameras can even factor in the colour of a subject, and draw on a bank of on-board images to compare the scene with before suggesting an exposure. These pattern metering modes – Evaluative on Canon cameras, Matrix on Nikon or simply Pattern or Multi-Segment on other cameras – can take the heat out of trying to work out an exposure when you need to work quickly, but you still may want to refine the exposure. Patten metering doesn’t know the mood you want to create, and it can still come unstuck when faced with very bright or dark scenes or when the subject is very small in the picture.

The easiest way to override the camera meter to make a picture brighter or darker is to use exposure compensation. You’ll find this option in your camera’s shooting menu and in its quick control screen. Alternatively, press the button marked ‘+/-’ on the camera and use your camera’s control dial or control pad to move the indicator along the scale in the viewfinder.

Reset exposure compensation to zero once you’ve finished, otherwise it will stay locked in the same position, even when you switch off the camera.

METERING FROM A MID-TONE Your camera’s spot meter is calibrated to a mid-tone value – so it will give a ‘correct’ exposure when it’s pointed at a midtone, such as a grey, rather than at black or white.

METERING FROM A DARK AREA Point the spot meter at an area that’s darker than mid-tone, and the camera will simply see this as a midtone that’s not receiving enough light, and attempt to brighten it up.

METERING FROM A BRIGHT AREA It’s the reverse if you point it at a bright area – the camera sees this as a midtone that’s getting too much light and will want to reduce the shot exposure accordingly.