A wide variety of ink printers is available today. They use ink-jet, bubble-jet, and other technologies, but in the end, they all perform the same function: spraying and dyeing the page with color. Originally, ink printers came in black only; now they are hard to find. Color dyes have become cheaper and easier to produce, and "photo-quality" has become a major selling point with ink printers. These printers are rated according to their resolution and color depth. Color depth is the range of colors that any given drop may represent. Unlike monitor resolution, which is a measurement of pixels across and down the screen, printer resolution is measured in dpi, the number of dots per inch (horizontally or vertically) that a printer can place on a page. Sometimes the dpi is the same both horizontally and vertically, such as 1200 dpi. Other times, the horizontal and vertical dpi differ—as in1440x720 dpi.
Printers usually use a four-color process, CMYK (cyan, magenta, yellow, and black), to produce various colors. Sometimes a three-color process is used, excluding the color black because it can be produced by mixing the other three colors. In a typical printer, each dot is composed of one or two drops of ink, giving about 15 colors.
Multiple drops of colors can also be placed on a single dot to produce more colors. Hewlett-Packard attempts to achieve better quality by increasing the color depth in its printers by layering multiple color drops within a single dot to create better image quality. Read the article on HP's color layering technology.
