Currently, at least six distinct kinds of colour printers can deliver prints of photographic or near-photographic quality. The following is a brief explanation of these printers:

Inkjet Printers
Inkjet printers use the "non-impact" principle of spraying tiny accurately aimed bits of ink on to paper. The ink, in a tiny resevoir behind each nozzle, is heated which forces the tiny drop through the nozzle. A variation of the thermal method is the piezo-electric system in which each nozzle is connected to a so-called piezo crystal, which forces a tiny drop of ink out of the nozzle when it reacts to an electrical charge.

Inkjet printers can produce very-high-quality images, and initial purchase prices are low. On the down side, print times, while constantly improving, are still slow relative to laser printers. Nevertheless, inkjet printers produce photographic-quality images much faster and at much lower cost than traditional photographs.

Laser Printers
Laser printing works by breaking an image down into a bitmap or a series of tiny squares. Next, the laser sweeps across a charged photoreceptor known as a "drum", sending a beam of light, leaving a positive electric charge which creates a mirror image of the original document on the drum. Colour is printed as a separate images or layers by mixing magenta, then cyan, then yellow, and finally black. The image is then transferred onto paper by applying negative charge that attracts the toner to the drum. The image is transferred to the paper when it comes in contact with the drum and, finally, heat and pressure are applied to the paper. This melts the toner, which contains small amounts of wax, and fixes it to the paper.

Laser printers are popular with businesses, where speed and lower per-print costs are important. However, high initial costs and less than perfect images make laser printers less attractive to most digital photographers.

Dye-Sublimation Printers
Designed for professional graphic artists, dye-sublimation printers operate like inkjet printers, except that they reach such high temperatures (upwards of 500 degrees Celsius) that allows colours to mix extremely well. Each colour--usually yellow, cyan, magenta and black--is printed individually, then mixed seamlessly on the paper.

This technique produces the highest quality images, making it ideal for professional graphic artists and photographers. However, the printers themselves are very expensive, costing ten or twenty times as much as inkjet printers. In addition, they require paper that is specially coated to receive the ink without bleeding, which poses an additional cost.

Thermal Wax Printers
Closely resembling the dye-sublimation method, thermal wax printers are designed especially to produce colour transparencies. The inks are wax-based, enabling them to adhere to the special transparency paper required.

These printers are designrd for producing transparencies, but they don't necessarily work for all-purpose colour printing as the level of detail they can capture is limited unless you will be creating transparencies from digital images. They are also expensive to buy, and materials can be expensive.

Solid Ink Printers
With the solid ink method, sticks of wax-based ink are heated until they reach liquid form. Then all three (cyan, magenta and yellow) or four (cyan, magenta, yellow and black) colours are squirted onto a transfer drum, mixing together to form a mirror image of the final image. Finally, paper is rolled across the drum to receive the final image.

Representing something of a compromise between inkjet and laser systems, solid ink printers are fast and require relatively cheap paper and ink (like laser printers), but their initial purchase price is relatively low (like inkjet printers). However, the quality of solid ink printers is not as high as that of either laser or inkjet printers.

Thermo-autochrome
Thermo-autochrome printing is most like traditional photographic processing. Thermo-autochrome paper is covered with three hidden layers of light-sensitive ink--cyan, magenta and yellow--each of which is activated at a certain temperature. As the special paper passes through the printer, tiny modules heat up tiny areas of the paper, activating the hidden colours one by one. Then an ultraviolet light passes across the paper, "fixing" the colours--that is, preventing the inactivated ink from developing.