Measuring the light

Most compact cameras have a small, separate window next to the viewfinder. This window holds a sensor that responds to light reaching it from the whole of the scene you can see in the camera viewfinder. This so-called ‘general’ light reading is accurate enough for average subjects. A general reading of the whole lot averages out all these differences, and the camera settings that are made have produced an exposure that is a good compromise for everything in the picture. Simply averaging the whole subject area in this way is not suitable for all subjects. Sometimes this approach can let you down, especially when the subject is full of mainly dark or light subjects. If your automatic camera has an exposure lock, you can first tilt the camera towards the area that you want to expose correctly so that the entire frame is filled. Then, by pressing the shutter halfway down or pushing the exposure lock button, the light reading is memorized and does not change when you compose the shot as you originally intended. With a camera set to manual mode you should use the same frame-filling procedure, adjust aperture or shutter speed to get a ‘correct exposure’ signal, and keep to these settings (even though over- or underexposure may be indicated when you recompose). Automatic cameras with an ‘exposure

compensation’ control will also allow you to override the aperture or shutter speed values and allow an increase or decrease of the overall exposure from that suggested by the camera’s meter. To double the exposure, for scenes with predominantly light subjects, you change the setting to ‘+1’. To reduce the exposure by half for scenes filled with dark objects, adjust the feature to ‘−1’. Most entry-level cameras use a so-called ‘center-weighted’ light measurement, designed to take more account of the broad central part of the picture, where the majority of main subjects are deemed to be placed. Advanced compacts and many SLRs offer a ‘multi-pattern’ form of metering light. Measurements are taken from several parts of the picture and the camera then calculates the exposure from the variety of brightnesses in the scene. The

more sophisticated versions of this system also take into account which segments should most influence the exposure for a given scene. This ‘matrix’ metering mode provides the most

accurate exposure measurements for the majority of scenes and should be the mode that you

keep as the default on your camera. Some models also contain a ‘spot’ reading mode, whereby just a tiny area, shown centrally in the focusing screen, measures the light. You can position this over any key part, such as a face, even when some way off. A spot reading is very accurate and convenient, provided you don’t let it stray to a completely wrong part of the scene.