Every camera has various different light metering options. It needs these to be able to get an acceptable exposure of a scene that’s neither too bright or dark for your taste, writes Andrew James and Jon Adams. It does this by reading the light reflecting off the subject you are photographing. The ‘exposure value’ metered is then converted into an aperture value and a shutter speed at a particular ISO setting. On DSLRs and mirrorless cameras, there are at least three ways of taking a light reading. These are Multi-pattern, Centre-weighted, or Spot, although manufacturers often call them different things to confuse us.
Multi-pattern: This is the most popular method. It takes multiple light readings from all over the scene to work out what the most likely exposure value would be in average conditions. This is called different things by different manufacturers, but Canon’s Evaluative, Nikon’s Matrix and Olympus’s Digital ESP all follow the same idea of measuring light from multiple areas to arrive at the exposure settings.
But because a camera doesn’t know what you’re looking at or what mood you want in the picture, multi-pattern metering won’t always get it right, so after checking the results, you’ll often need to adjust it with Exposure Compensation to make the picture brighter or darker and reshoot to get the look you want.
Foto-Buzz advice: Use for all general photography such as landscapes and wildlife as a default setting but be prepared to use exposure compensation from time to time. If you really don’t want to switch between metering modes, use this and regularly check your histogram.
Centre-weighted: This is a traditional method that biases the light reading towards the centre of the frame. It’s a throwback to film cameras, but as it can be fooled by bright or dark areas in the middle of the scene, it’s arguably less reliable than multi-pattern metering, and also often requires Exposure Compensation to get to the brightness needed.
Foto-Buzz advice: Leave well alone! In fact, we’re not sure why it’s still featured on every camera! We know it’s the traditional metering mode but times have moved on.
Spot: This is the most precise option available, allowing the photographer to take a reading from a very specific area of a scene – which could be under the active AF target point or it might the centre of the frame. If this area is a midtone, and is in the same light as the rest of the scene, you will get an accurate exposure. But, if it’s brighter than a midtone, you will underexpose the shot, and if it’s darker than a midtone, you will overexpose the shot. Spot metering allows you to bypass what the camera maker ‘thinks’ is the correct exposure, and make your own decisions, based on how you want your shot to look. But to use it effectively, you have to be good at knowing what a midtones actually is. All natures reds are approximate midtones, so think of things such tomatoes, red roses, or even a red Gore-tex jacket creeping into your landscape. If none of these exist, a tarmacked surface would do, or you could even use a clear blue sky about 25 degrees up or a patch of green grass. Better still carry a grey card!
For most photographers, spot-metering is used in ‘difficult’ lighting conditions – such as shooting a shaded subject against a much brighter background. If you Spot meter from a midtone in the same shade as the subject’s face (say a midtone piece of clothing or that purpose-built grey card with average reflectance), then the brightness of the background will be ignored and bleached out, and a good exposure of the subject’s face will be the result.
In difficult lighting, spot-metering is much quicker to employ and more reliable than other hit-and-hope methods, and with practice, may become your go-to option. However, if used without care and attention, you might find your exposures become a bit erratic.
Foto-Buzz advice: Great for portraits but remember not all skin tones are the same so try to meter off midtoned clothing being worn by your subject in the same light. But it can rescue you in tricky lighting such as silhouettes, or ultra-high contrast conditions, as long as you can find a midtone somewhere between the extremes.
Images Above: In shot one we’ve spot metered from the face which is brighter than a midtone, so the whole image is slightly underexposed. The second shot we’ve corrected by spot metering from grey card so the shot is well-exposed.
With any metering mode, including Spot, it’s always a good idea to use it in conjunction with your camera’s Histogram display, as this will give you an objective, graphical overview of the distribution of tones in the scene.
Spot the project
To really get to grips with Spot metering, here’s something you can go out and try with your camera. Set the metering mode to Spot metering and then use it exclusively for a session – looking out for those naturally occurring midtones within the same the light, unless you happen to have an 18% grey card handy. This will give you the confidence to use Spot when it’s really needed.