Pixels per inch
Also called: ppi, pixel density, pixel density or pixels per centimeter(ppcm)
The sharpness of a digital image is expressed in the number of pixels per inch (PPI). Sometimes it is also stated as number of pixels per centimeter (PPCM). The number of pixels is determined by the size of an individual pixel and their spacing.
The higher the pixel density, the less distinguishable the individual pixels are and the sharper the image can be displayed. This makes PPI an important characteristic for comparing computer monitors, televisions, cameras and scanners.
Sharpness of images and dpi
Sometimes the sharpness of image files is also expressed in pixels per inch. This assumes the number of pixels per inch when the image is displayed at "actual size. This can be particularly relevant when the image is to be printed. Here more detail is desired than in a digital reproduction.
The sharpness of printers and printing itself, by the way, is more often expressed in dots per inch(DPI). The higher the number of dots per inch, the higher the resolution and the more detail can be printed.
