Scanners and Cameras
"PPI" or "pixel density" may also be used to describe the resolution of an image scanner. In this context, PPI is synonymous with samples per inch.
In digital photography, pixel density is the number of pixels divided by the area of the sensor. A typical DSLR circa 2011 will have 1–4.5 MP/cm2; a typical compact will have 20–60 MP/cm2. For example Sony Alpha 55 has 16.2 megapixels on an APS-C sensor having 4.5 MP/cm2 since a compact camera like Sony Cybershot DSC-H70 has 16.2 megapixels on an 1/2.3" sensor having 60 MP/cm2. Interestingly, as can be seen here, the professional camera has a lower PPI than does a compact, because it has larger photodiodes due to having far larger sensors.
Read more about this topic: Pixel Density
Famous quotes containing the word cameras:
“While the music is performed, the cameras linger savagely over the faces of the audience. What a bottomless chasm of vacuity they reveal! Those who flock round the Beatles, who scream themselves into hysteria, whose vacant faces flicker over the TV screen, are the least fortunate of their generation, the dull, the idle, the failures . . .”
—Paul Johnson (b. 1928)