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:
“Guns have metamorphosed into cameras in this earnest comedy, the ecology safari, because nature has ceased to be what it always had been—what people needed protection from. Now nature tamed, endangered, mortal—needs to be protected from people.”
—Susan Sontag (b. 1933)