A number of methods for making digital photographs are used. Some of these technologies include the thermal-dye transfer, inkjet, thermal-wax transfer, and printers that use silver-halide photographic paper to produce digital images. Color copiers can also be used to print digital images to provide suitable quality at high speed and relatively low cost. Like most electronic equipment, a large variety of printers are available on the market. They range from hundreds to thousands of dollars.

Most printers used for making color prints from digital images use three colors: cyan, yellow, and magenta (CYM). Some printers match the full cyan, yellow, magenta, and black (CY MK) process.

Located between the printer and the computer is a RASTER IMAGE PROCESSOR (RIP) or a PAGE DESCRIPTION LANGUAGE (PDL). This is a software and hardware configuration that permits information to flow to the printer so the printer knows where to place the image on the paper.

Thermal-Dye Transfer Printers

Thermal-dye transfer printers are often called dyesublimation or dye-diffusion thermal-transfer printers. This system provides high quality and an environmentally safe method of transferring images to print and transparency materials without using chemical fig. 3-10 .

The thermal-dye transfer printing process uses thousands of tiny heating elements that come in contact with "donor ribbons." Each donor ribbon releases a gaseous color dye when heated. Three-color printers have cyan, magenta, and yellow ribbons (CMY); four-color printers also include a separate black ribbon (CMYK). The amount of heat from each element

Figure 3-10.-Kodak 7720 thermal-dye transfer printer.

controls the amount of dye being transferred to the print material. The blend of the gaseous colors creates a continuous-tone image.

The quality of a thermal-dye transfer print resembles a print made from conventional silver-halide paper. The resolution of thermal-dye transfer printers ranges from 160 to 300 dpi. Resolution is limited by the thermal printing head. Thermal-dye transfer printers can produce prints from 3.5 by 5 inches up to 14 by 17 inches.

Inkjet Printers

Inkjet printers are used in a variety of situations from newsprint to transparency materials. Inkjet printers use cyan, magenta, yellow, or black streams of ink to produce images. Inkjet printers today are capable of producing excellent continuous-tone color prints by using variable-size dots of ink that are precisely controlled. Inkjet printers are nonimpact printers that use droplets of ink. As the head of the printer moves across the surface of the paper, it shoots a stream of tiny electrostatically charged ink drops at the paper.

Color Copiers

Color copiers were originally designed strictly for copying color originals. Today, however, color copiers have the added capability of copying transparencies and being connected directly to imaging workstations through an interface. This interface accepts digital signals to produce color photographs.

Color copiers are capable of producing prints with a true photographic appearance. One minor drawback to prints produced on color copiers is they are printed on plain, bond paper stock Color copiers use a laser device that fuses toner to paper to create the image. Some color copiers, such as the Canon Color Laser Copier 500 fig 3-11 , can be used as a flatbed scanner in addition to providing high-quality color images directly from computer files. The resolution of such color copiers is 400 dpi on standard copier paper. Thermal-Wax Transfer Printers

Thermal-wax transfer printers operate on the same principle as thermal-dye transfer printers. Thermal-wax transfer printers use cyan, magenta, and yellow wax type of pigments instead of ink to produce images.

Figure 3-11.-Canon 500 color copier with the EF1 Fiery controller.

Thermal-wax printers are designed to produce clean, bright colors; however, they have a limited range of colors because these printers are only capable of producing colors that are one-bit per color deep. These printers are relatively inexpensive and can produce large prints quickly.