24 June 2009
A pixel can be defined as the smallest element of information in an image, thus the word 'pixel' comes from combining the two words of picture and element. A megapixel, therefore, is defined as 1 million pixels, or 1 million picture elements.
The terms pixel and megapixel are not only used to describe the number of pixels in an image, but also to define the number of image sensor elements or image capturing capability of modern digital cameras.
For example, a digital camera such as the Canon Digital IXUS 980 IS is said to have 14.7 megapixels, this means that the camera features a CCD sensor which is capable of capturing images with up to 14.7 million pixels. Actually, the maximum resolution image that the IXUS 980 captures is 4416 x 3312, which equals 14,625,792 pixels.
Most compact digital cameras use a charged coupled device (CCD) to capture the pixels. These consist of an array of single sensor elements, each of which capture a measured light intensity level. Colour is calculated with the help of a patterned colour filter mosaic of red, green and blue. The single sensor elements can then detect the relative proportions of each primary colour. Put simply, larger megapixel cameras just have more of these single sensor elements in the CCD, resulting in higher picture resolution.
Probably, the vast majority of compact digital camera users don't require such high resolutions. Anything above 8 megapixels is usually in excess, unless we are taking photos to be blown up to poster size, the resolution really isn't noticeable when viewing on a standard PC monitor. Many images have to be shrunk down to much lower megapixels anyway, for emailing to friends or storing to disk.
Don't just look at megapixels when buying a digital camera, there are far more important things to consider, such as image stabilisation, exposure levels, shutter speeds, optical zoom capability, focus range and manual control functionality.
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