DPI vs LPI

Dots Per Inch (also known as DPI) is literally a measurement of the maximum number of dots any printer has access to per inch. The dots reference the unit in which all printers and computers are measured, namely, binary code. As such, each dot is either off or on. These dots make up a grid pattern which can only print in black and white. There are no colors or shades of colors (such as grey). To accomplish the appearance of grey on a printed sheet, the printer uses an optical allusion with dots of varying sizes – placing the dots next to each other, and printing in high resolution, gives the appearance of grey.

Lines Per Inch (also known as LPI) is a measurement of the number of rounded dots that are in an inch. LPI is also known as a screen, and is given its name because each rounded dot has a centre point that’s created in varying sizes. This variation depends on the shade of grey used, and assigns the centre points units of lines per inch.

As dots make up the components of a grid, all rounded dots are formed from a distinct pattern of squared dots. The appearance of roundness depends on the resolution of one’s computer, and/or printer. The LPI is directly related to the DPI, and DPI is directly related to resolution. Depending on the resolution, one may acquire a picture that seems ‘grainier’ than others – that is, pixilated. For instance, in order to get a dot that actually appears round rather than square, or pixilated, one must have a DPI of at least 600. A glossy magazine is usually printed with an LPI of 150; as it relates to DPI, which means that the resolution was 2400 DPI or higher.

LPI is not solely associated with dots. It is usually measured at angles. The color black is usually placed at a 45 degree angle – another optical allusion so that the viewer does not see a grid, but rather sees the color black.

Summary:

1. DPI measures the maximum number of dots a printer prints per inch; LPI is a direct measurement of the number of rounded dots in an inch.

2. In DPI, dots make up a grid shape, and are squared on the grid; in LPI, lines are made up of the multiple squared dots (that eventually make a rounded dot).

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