what is “NPI” in inkjet

Posted: June 26, 2017 in Color

The Droplet – Print Resolution and DPI: A Brief Review
Print resolution is the capability of a printing system to reproduce image detail. There are two major factors that influence print resolution:
– The DPI (dots per inch) of a print system (which is characterized by a printhead or group of printheads).
– The level of sharpness and contrast, which is a component of the drop size. This is directly related to how an image is seen by the human eye.

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Many factors contribute to the overall performance of a printhead: drop size(s), nozzles per inch (NPI), drop volume consistency, accuracy of drop placement, and print system integration. In addition, consideration of the viewing conditions, contrast, and viewing distance will help determine optimal print resolution for a print. If a higher print resolution cannot be seen by the naked eye, the benefit of that additional resolution is lost.
Inkjet printheads are distinguished by their nozzles per inch (NPI). Also known as native DPI, this is the rectangular grid of possible printable dots defined by the nozzle distance along the axis of the printhead, and by the speed and print frequency along the axis of the media motion. The NPI value of a printhead determines the location of dots, but does not actually determine the maximum possible print resolution, or size of the printed dot.
Printers also have the factor of effective DPI. This is the smallest incremental distance that a printer can shift from the middle of one point to the middle of the next. When resolution is increased on the axis of the media, this in turn increases the effective DPI, which also impacts the level of detail. DPI can also essentially be doubled by interleaving multiple printheads within the configuration.

source: CET Color

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