3. Sensor Size, Photosites, Pixels, Et Al

There are not many manufacturers in the CCD market. Sony, Panasonic and Philips are the main players, and you will find their sensors on most cameras, no matter the brand. Downstream sensor "buyers" develop their own electronic data processing systems, and this is why there are differences in the end quality (apart from the lenses, of course).

The currently predominant sensors have a diagonal of 1/1.8". On this (small) surface, the manufacturers align a quantity of light-sensitive photosites. The more photosites there are, the more pixels there will be in the end image (note: the number does not match exactly - there are usually more photosites than pixels). The trouble is that increasing the resolution causes space problems. While it is easy to align a million photosites on the surface of the sensor, it is a lot harder to align two, three or five million! The more photosites you have on the same area, the smaller they are and the less empty space there is, and, what's more, this generates electronic parasites. In practice, the result is a loss of sensitivity and an increase in image noise (the unpleasant grainy look due to parasite pixels, mostly in the darker areas of the image, but sometimes throughout). To overcome this, the manufacturers also work on electronic processing and sensor size. Some cameras now have bigger sensors measuring 2/3" (e.g. the Nikon Coolpix 5000 and Minolta Dimage 7). Which diagonal will be adopted in the end is anybody's guess.