Despite today's options for viewing and sharing images on a computer screen, many people still want or need prints.

Consumers can opt for the convenience of dropping film off at a retailer or ordering prints online, the creativity of using in-store kiosks to personalize or create gifts with images, or the control of using home printers to adjust and create prints. Commercial and medical users can choose from a variety of alternatives, based on the quality, cost and finished product needed for the job.

Kodak's expertise in color science and thin-layer coating is key to the technologies commonly used to print pictures and images today. These technologies include the following:

Silver Halide

The no-hassle scenario goes like this: You drop off a roll of film at your local store and within a couple of days or even an hour, you have high quality prints and negatives that will last for generations.

How does it work? As in capturing images on film, light is the key. Light shines through a film negative to project a "positive" version of the image on a special paper. The paper is coated with light-receptive silver crystals and compounds that, when mixed with chemical developers, form dyes to reproduce the image. In light or white areas, the silver is not activated and is rinsed from the print during development.

In black-and-white printing, photographic paper includes a single layer of the light sensitive crystals and compounds. In color printing, the paper includes separate layers for cyan, magenta and yellow -- the primary pigments that combine to print any color.

After exposure, a series of chemical solutions are used to develop the image, stop development and fix the image for stability.

Today, film negatives can also be scanned, with images printed directly onto photo paper using lasers and LEDs. Kodak's new Perfect Touch processing technology digitally enhances pictures before printing to reveal more vibrant colors, richer detail and fewer dark shadows. This can greatly improve prints of poorly exposed or backlit pictures.

Inkjet Printing

Inkjet technology is commonly used to print photographs at home. Input starts as a digital photo, or a traditional photo scanned into a computer. A series of printheads sprays droplets of ink onto paper to re-create the image, typically using cyan, magenta, yellow and black colors. The printer electronics control the position of the printhead and ejection of droplets to dispense the ink in the right amount, at the right time, and in the right positions. Some inkjet printing -- especially printing of text documents -- is done on plain paper. For printing pictures, Kodak and others offer special photo inkjet paper that gives the look and feel of a photographic print. Layers of polymers coated onto the photo paper help reduce the amount inks "bleed" into one another or into the paper. This avoids wrinkling, improves image quality, and gives the print a glossy look. The polymers also interact with the inks to make the image last longer and resist fading.

Kodak inkjet picture papers.

Wide format inkjet printing is used to create large signs and posters of near photographic quality, principally for business and commercial markets.

Thermal Dye Transfer

In this process, a dye-bearing ribbon is placed on a specially coated paper and heated by a print head. The heat causes dye to move from the ribbon to the paper to reproduce an image. The dye ribbon has four separate panels -- three contain dyes for the primary colors (cyan, magenta and yellow), the fourth contains a clear coating that is used to improve image stability and longevity. In fact--like silver halide prints--thermal prints should last for generations given the right storage conditions.

EASYSHARE printer dock.

Because in thermal printing the dyes penetrate the paper instead of just being painted onto its surface (like inkjet), thermal prints don't require drying time, and tend to resist fading. Also, because the dye is continuously transferred to the paper, rather than laid down as individual dots, thermal produces images with finer density gradations, and a more photographic appearance.

Kodak uses thermal printers in its picture maker stations -- kiosks that allow you to make prints and enlargements from existing pictures, film negatives, digital memory cards, and a number of other electronic media. It is also the technology used in the new EasyShare printer docks, which produces durable 4 x 6-inch prints form a digital camera--with or without a computer. You simply place the related EasyShare digital camera into the dock and request a print, which is delivered in as little as 90 seconds.

In high-precision applications, as in medical imaging or the graphics/printing industry, thermal printers use a laser to heat the dye ribbon--more precisely transferring dye particles to the paper/media. For example, Kodak's DryView laser medical imaging systems print diagnostic images from ultrasounds, computed tomography (CT) scans, magnetic resonance imaging (MRI) and other such 'modalities.' Because the thermal process is dry and does not require chemicals for processing, hospitals don't need to factor plumbing or chemical use into where they install these printers.

Commercial Offset Printing

In graphic arts, images are often printed on presses using an "offset" process, which means an image is transferred to a series of intermediate drums and rollers before reaching paper.

In offset printing, an image is first formed on a thin sheet of aluminum known as a printing plate. This serves as a durable "master" that is used to transfer the image many times. making offset printing suitable for printing large quantities (usually more than 500) of an image at one time.

The printing plate is wrapped on a cylinder, and as it rotates, it comes in contact with ink. Based on the image, regions of the plate chemically attract or repel the ink. The inked plate then transfers the image to a roller, which finally transfers the image to a sheet of paper.

The same process repeats for each color in the printing press. Most colors are formed by a sequence of cyan, magenta, yellow, and black printing. By controlling the placement, size and intensity of the dots of ink being printed, this sequence can replicate most colors. Specialty colors, however, may be additionally printed.

Kodak, though its Kodak Polychrome Graphics (KPG) joint venture, is a leading supplier of printing plates for the printing industry. KPG supplies both conventional printing plates, which are imaged using traditional photographic processes, and digital printing plates, which are imaged directly from a computer file.

Electrophotography

Electrophotography uses a laser to place an electrical charge on a metal drum. The charge either attracts or repels colorant particles (dry powders of cyan, magenta, yellow and black colors) to create an image that is eventually transferred to paper. A separate laser/drum station is used for each color that will comprise the image. Once the toner has been transferred to paper, heat and pressure bond it to the paper surface.

The electrophotographic process is ideal for creating short-run and customized printed pieces (like catalogs tailored for individual customers) because it replaces a static printing plate with an imaging drum that can be economically re-written with a new image for each print.

Kodak's NexPress unit uses electrophotographic technology in its NexPress 2100 digital production color press. Incorporating more than 300 patented innovations, the 2100 has been recognized by industry organizations for its high quality and technical excellence.