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Photo Printing

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With the popularity of digital cameras, more and more people are taking more and more photographs. In fact despite scare-mongering stories about "the end of history" and "the death of photography", the truth is that there are more photos being taken today than ever before. However most of those photos will never be seen by anyone except the person who took them, because hardly anyone prints their photos any more. This is very odd, because many people have home computers with photo-quality printers that are more than capable of producing first-class prints from almost any digital photograph. Printers are ludicrously cheap, to the point that when your printer runs out of ink it’s almost cheaper to throw it away and buy a new one than it is to buy more ink.


Types of printer

There are two main types of photo printer in common home use. By far the most common is the inkjet printer, which includes most of the models from most of the major manufacturers, which basically means Epson, Canon, Lexmark and Hewlett Packard (Dell printers are made by Lexmark). They operate off a fairly simple principle. The printer has a head which moves rapidly over the surface of the paper. In this head are a number of tiny nozzles, through which minute droplets of ink are forced, spraying onto the paper in tiny but precisely measured quantities, as many as 30,000 droplets per second. The actual method by which the ink is forced out of the nozzles varies from one manufacturer to another, with Canon, HP and Lexmark favouring a thermal system which boils the ink at the print head, using the bursting bubbles to spray the ink (hence Canon’s BubbleJet name), while Epson uses a more complex and expensive but also more versatile piezo-electric compression system.



Usually when printing a photo it will take several passes of the head over each line to build up the full colour image one colour at a time, which means that photo printing is much slower than printing a text document, and also uses up a lot more ink.

While some older printers use one ink cartridge for black (primarily for text printing) and another for three additive primary colours, a recent trend is for printers to use multiple colour cartridges, in some cases as many as eight. This has two main advantages. The addition of lighter shades such as grey, light magenta and light yellow means that the printer is better at reproducing subtler colour variations, especially in skin tones, and is also better at reproducing shadow and highlight detail. The other advantage is that if one colour runs out you don’t have to throw away a cartridge that might still have plenty of the other colours left. You just replace the one that’s empty. This is a lot less wasteful, and also works out cheaper in the long run.



The other main format of home printer is the dye-sublimation type, often shortened to “dye-sub”. This technology is popular for smaller dedicated photo printers, such as Kodak’s EasyShare range of docking printers. Most print out at sizes no larger than 6 x 4 inches, although some A4-sized models do exist, such as the Olympus P-440.



Dye-sub printers work in a completely different way to inkjets. They use a ribbon carrying coloured panels of special dye, and this dye is transferred to specially treated paper by a thermal process. The ribbon will have to be replaced after a specific number of uses, so paper and ribbons are usually sold together as a pack, with just enough paper for the lifetime of the ribbon. Usually the ribbons carry cyan, yellow and magenta dye, and the image on the paper is built up one colour at a time. Dye sub printers are usually slower than equivalent-sized inkjet printers, and are usually also more expensive to buy and run. They are more wasteful of resources, since the ribbons cannot be reused despite there frequently being a lot of dye left after use. The main advantage with dye-sub printers is that they do produce almost perfect photo-quality prints, since the image is built up in transparent layers rather than a pattern of tiny dots. Dye-sub prints may also be more resistant to fading.

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