[COLOR=darkgreen][B]No.3[/B][/COLOR] [COLOR=black]Today, a concise explanation of the commonly featured exposure metering options in modern digital cameras.[/COLOR]

[B][COLOR=darkgreen]Metering coverage[/COLOR][/B]

[B][COLOR=darkgreen]Average:[/COLOR][/B] The the brightness of the entire area of the frame is averaged. The problem with a simple mode like this is that extreme brightness or darkness in small areas of the scene may cause the most interesting parts of the picture to be wrongly exposed. Fewer cameras now use this kind of mode, preferring a segmented or matrix system, covered further down the page.

[COLOR=darkgreen][B]Centre-weight:[/B][/COLOR] This is rather like the Average mode (above) but concentrates on the central portion of the frame, which is often what you are most interested in. This can be useful, especially if the margins of the frame have a very different brightness to the centre.

[B][COLOR=darkgreen]Spot:[/COLOR][/B] In a classic sense, a spot meter may only be sensitive to as little as 1% of the frame, though in modern times a spot mode can often mean an area up to 5% of the frame. By restricting the meter to a very small area you can very precisely select the correct exposure for where only a small area matters. An obvious example is where a subject is in danger of being silhouetted by a lot of light in the background. Lining the spot meter point up with the subject avoids any bias from the surrounding brightness and you should get the correct exposure for that area. Spot mode must be used with care, because it can cause big exposure inaccuracies if it isn't used precisely.

[COLOR=darkgreen][B]Matrix/segmented (also known as Evaluative mode): [/B][/COLOR]This type of mode will cover most of the frame. The metered area is segmented, matrix fashion, into dozens of separate areas. The camera will then evaluate the readings from all the segments and discard any that are significantly above or below the majority of the rest. This is the best general purpose mode to use as it works better to ensure that extreme differences of brightness in the frame don't affect the main parts of the scene. It's not fool-proof, however, so the use of Centre Weight, or Spot, will be more reliable under certain lighting conditions.

[COLOR=darkgreen][B]Tomorrow: Auto, Program, Shutter, Aperture, and Manual mode systems explained.[/B][/COLOR]


[COLOR=black][I]Incidentally, please don't hesitate to post a question about this Daily photo tip if you have one![/I][/COLOR]