Editing Pixel density (section)

== Printing on paper ==
Printing on paper is accomplished with different technologies. Newspapers and magazines were traditionally printed using a [[halftone]] screen,<ref>{{cite web|title=Haltone: Atlas of Analytical Signatures of Photographic Processes|url=https://www.getty.edu/conservation/publications_resources/pdf_publications/pdf/atlas_halftone.pdf|publisher=The Getty Conservation Institute|year=2013}}</ref> which would print dots at a given frequency, the screen frequency, in [[lines per inch]] (LPI) by using a purely analog process in which a photographic print is converted into variable sized dots through interference patterns passing through a screen. Modern inkjet printers can print microscopic dots at any location, and don't require a screen grid, with the metric [[dots per inch]] (DPI). These are both different from pixel density or pixels per inch (PPI) because a pixel is a single sample of any color, whereas an inkjet print can only print a dot of a specific color either on or off. Thus a printer translates the pixels into a series of dots using a process called [[dither|dithering]]. The [[dot pitch]], smallest size of each dot, is also determined by the type of paper the image is printed on. An absorbent paper surface, uncoated recycled paper for instance, lets ink droplets spread — so has a larger dot pitch.<ref>{{cite web|title=Understanding Resolution and the meaning of DPI, PPI, SPI & LPI|url=https://www.ideastraining.com/PDFs/UnderstandingResolution.pdf|author=David Creamer|year=2003}}</ref>

Often one wishes to know the image quality in pixels per inch (PPI) that would be suitable for a given output device. If the choice is too low, then the quality will be below what the device is capable of—loss of quality—and if the choice is too high then pixels will be stored unnecessarily—wasted disk space. The ideal pixel density (PPI) depends on the output format, output device, the intended use and artistic choice. For inkjet printers measured in DPI it is generally good practice to use half or less than the DPI to determine the PPI. For example, an image intended for a printer capable of 600&nbsp;dpi could be created at 300&nbsp;ppi. When using other technologies such as AM or FM screen printing, there are often published ''screening charts'' that indicate the ideal PPI for a printing method.<ref>{{cite web|title=Understanding Resolution and the meaning of DPI, PPI, SPI & LPI|url=https://www.ideastraining.com/PDFs/UnderstandingResolution.pdf|author=David Creamer|year=2003}}</ref>

Using the DPI or LPI of a printer remains useful to determine PPI until one reaches larger formats, such as 36" or higher, as the factor of visual acuity then becomes more important to consider. If a print can be viewed close up, then one may choose the printer device limits. However, if a poster, banner or billboard will be viewed from far away then it is possible to use a much lower PPI.{{cn|date=May 2023}}

[[Image:Square 200x200.svg|right|frame|The outside of the square shown above is 200&nbsp;pixels by 200&nbsp;pixels. To determine a monitor's ppi, set the OS [[1:1 pixel mapping|DPI scaling setting at 100%]] and the browser's zoom at 100%, then measure the width and height, in inches, of the square as displayed on a given monitor. Dividing 200 by the measured width or height gives the monitor's horizontal or vertical ppi, respectively, at the current screen resolution.]]