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Scanners and cameras. "PPI" or "pixel density" may also describe image scanner resolution. 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 2013, has 1–6.2 MP/cm 2; a typical compact has 20–70 MP/cm 2 .
He did not change the subdivisions (1 inch = 12 subdivisions = 72 points), but defined it strictly in terms of the royal foot, a legal length measure in France: the Didot point is exactly 1 ⁄ 864 of a French foot or 1 ⁄ 72 of a French inch, that is (by 1799) 15 625 ⁄ 41 559 mm or about 0.375 972 mm. Accordingly, one Didot point is exactly ...
The size of a screen is usually described by the length of its diagonal, which is the distance between opposite corners, usually in inches. It is also sometimes called the physical image size to distinguish it from the "logical image size," which describes a screen's display resolution and is measured in pixels.
For a pixel pair (one white and one black pixel) this gives a pixel density of 128 pixels per degree (PPD). 6/6 vision is defined as the ability to resolve two points of light separated by a visual angle of one minute of arc, corresponding to 60 PPD, or about 290–350 pixels per inch for a display on a device held 250 to 300 mm from the eye. [24]
The pica is a typographic unit of measure corresponding to approximately 1 ⁄ 6 of an inch, or from 1 ⁄ 68 to 1 ⁄ 73 of a foot. One pica is further divided into 12 points. In printing, three pica measures are used: The French pica of 12 Didot points (also called cicero) generally is: 12 × 0.376 = 4.512 mm (0.1776 in).
An image that is 2048 pixels in width and 1536 pixels in height has a total of 2048×1536 = 3,145,728 pixels or 3.1 megapixels. One could refer to it as 2048 by 1536 or a 3.1-megapixel image. The image would be a very low quality image (72ppi) if printed at about 28.5 inches wide, but a very good quality (300ppi) image if printed at about 7 ...
The nautical mile (nmi) was originally defined as the arc length of a minute of latitude on a spherical Earth, so the actual Earth circumference is very near 21 600 nmi. A minute of arc is π 10 800 of a radian . A second of arc, arcsecond (arcsec), or arc second, denoted by the symbol ″, [ 2] is 1 60 of an arcminute, 1 3600 ...
Pixels can be used as a unit of measure such as: 2400 pixels per inch, 640 pixels per line, or spaced 10 pixels apart. Pixel art The measures " dots per inch " (dpi) and " pixels per inch " (ppi) are sometimes used interchangeably, but have distinct meanings, especially for printer devices, where dpi is a measure of the printer's density of dot ...