Canon Digital IXUS 850 IS

Sharpness

Sharpness is potentially the most important element of a picture. The sharper a shot, the more depth and clarity it will appear to have. Sharpness is a term used to describe the boundary between one section of colour and another. The more defined this border is, the sharper the shot. It is measured by comparing the distance it takes a pixel to change from one colour value to the other. All cameras will blur to some extent, but in good models it won't be noticeable until you really zoom in to extreme levels. The higher the value, the better the camera; anything over 1300 should be considered excellent.

Chromatic Aberration

Cameras with Chromatic Aberration are often attributed as having poor sharpness, but this is not the case at all. Chromatic Aberration is caused by light refracting at incorrect angles as it passes through the lens. It occurs around the edge of a shot and presents itself as colour fringing, which can destroy the clarity in those areas. Chromatic Aberration is measured in terms of its distance from the centre. A lower percentage is good. Anything below .05 should be considered fairly good.