PUB2000: How to Control Lines Per Inch (LPI) From Publisher (212565)

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What is Lines Per Inch?

The term, lines per inch, comes from a photo-mechanical process called halftoning. Halftoning is a method of breaking up shades of gray into dots of different sizes. True halftones are created by photographing continuous tone artwork onto high-contrast film through a halftone screen. Halftone screens were originally created by etching a grid of lines onto optical glass. The number of etched lines per inch is where the term lines per inch comes from.

In a true halftone, all the dots are the same distance apart. You achieve the effect of light and dark by increasing or decreasing the size of the dots. The larger the dots, the smaller the amount of white space around them and the darker that area of the paper appears when you view it at a distance. The higher the lines per inch, the closer together the dots appear.

Electronic printers do not print true halftones. Electronic printers print dots of only a single size (measured in dots per inch or dpi); instead of changing the size of their dots they change the distance between the dots. Many electronic printers simulate true halftones by clustering their tiny fixed-size dots in such a way as to give the appearance of an array of (larger) equidistant dots of different sizes.

Setting Lines Per Inch

If you are printing to a PostScript printer, you can change the lines per inch setting. To define lines per inch, follow these steps:

1. On the File menu, click Print.
2. Click Advanced Print Settings.
3. Click the Device Settings tab.
4. In the Screens section, click to select the Use Custom Settings Below.
5. Type the desired lines per inch in the Frequency box next to the color(s) you will be printing. If you are not printing color separations, the only color you need to change is black.