Part 5 - Metering
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Metering is a process which involves the camera taking a light level reading from the scene and selecting the appropriate combination of aperture and shutter speed to set the required exposure value. Various modes are offered to allow the user to select the most suitable one for the specific lighting conditions These can then be changed manually via use of exposure compensation metre if required. There are various types of metering which can be set, and these change the way the light levels are read by the camera.
Here a metering is taken from the whole of the scene first, then the central spot. The result is the average reading, but with extra weight given to the central part. Some cameras allow the user to change the amount of weight given to the central area but as a general rule, around 60 to 80 per cent of the sensitivity is directed towards the central part of the image, making it a good choice for portraits.
Using centre-weighted metering has given the desired result balancing the bright backlighting and the dark foreground of the subject.
Spot metering has resulted in the picture being far too light, as the reading has been taken from the dark central strip of the image.
Spot metering takes a reading from a very small part of the image (between 1 and 5 per cent), and ignores the exposure of the rest of the scene. While this area is usually in the middle of the scene, some cameras allow the user to select a different part of the image from which to take a reading, or to recompose the shot after taking a reading. Spot metering is good choice for high contrast and backlit scenes but needs to be used with care, and aimed at an area that will form the mid-tone part of the final image.
Here zone metering was not
the appropriate metering type to use,
as the bright backlighting made the
subject appear too dark.
A type of metering first introduced by the Nikon, zone is a type of metering which takes readings from several different areas - or zones - within the scene to produce a calculated average. The number of different zones used can vary dramatically from one camera to another, but the end result is usually just an average of them all. This is useful for general scenes with low contrast.
There are other various types of metering, but these tend to be a variation of the three types mentioned above.
Having different metering modes available becomes more useful for when you start to progress to more advanced photography, for example, subjects backlit by the sun. This is when modes such as Spot or Centre -weighted metering will become appropriate.
In next week's guide we will be looking at using flash in more detail, and the different types of flash that are available.
All images in this guide were taken with the Canon EOS 400D